Tliis invention relates to a device, which is arranged to be used for heating and/or derubberizing or similar of objects. In this respect, the objects consist at least partly of metal. The device comprises a core and at least one coil, which is connected to a current source to produce induction of a magnetic field, the flux of which is intended to follow the said core. Thus, the arrangement is intended to be rased in electro- technical methods for heating and/or derubberizing of objects, i.e. by generating magnetic fields.

By using such a method the heating time for preheating of moulding tools within, for example, the rubber industry can be considerably reduced, as well as preheating of parts of metal included in objects. Furthermore, the method can be used for derubberizing of rubber-metal objects, i.e. for a separation between rubber and metal. A further field of application is in shrink fit operations between objects of metal.

There is a need to simplify devices of this kind and to reduce leak fluxes of magnetic fields, to ensure that none unintended induction current arise, to reduce heating losses and to relieve the core from loadings of the objects, which are to be heated.

In a previous known device the objects to be heated are supported by the poles of the core, i.e. that the object is to be introduced between the poles of the core simultaneously as a coil is arranged around the end portions of the poles of the core. In this connection the core has to take the loading from the object, which is also difficult to place in the device, as the said coil prevents accessibility between the poles of the core. Besides these inconveniences, the known device is limited in its use, as objects with proportionately heavy weight and/or large di en-sion cannot be supplied and treated or be heated in the device. Further-more, the known device lacks devices to reduce the heating losses and leak fluxes.

A device in accordance with the present invention fulfills, however, the requirements made, simultaneously as the inconveniences with the known device are eliminated. One object of the device in accordance with the invention is thus to be able to heat objects with considerable weight and which also are voluminous and=in that respect completely unload the core

or its poles from loadings of objects. Another object with the invention is to effect an improved contact between different parts of the core and in that respect i.a. to reduce the heating losses. A further object with the invention is to make it easier to supply the objects which shall be heated or treated. The device in accordance with the invention is caract- erized in that the device comprises a table with a disc-shaped element, consisting of electrical insulating material. Further in that a part of the core is arranged displaceable.

In one embodiment of the device in accordance with the invention the table is arranged around a portion of the core, for example around one of the poles or a stationary pole of the core, and shews an opening through which the core can extend.

According to an another embodiment of the device in accordance with the invention, the table or the disc-shaped element is arranged on a support¬ ing frame of a first material, as metal, and that the supporting frame shows a breakage, in which the said first material is lacking in the supporting frame, but which breakage is overlapped or restored by means of a frame piece of a second material, consisting of insulating material.

In an additional embodiment of the device in accordance with the inven¬ tion the device comprises a press device which is arranged to press the displaceable part of the core against the core. The pressing of the said part of the core against the core is in the device meant to be done before that current from a current source is supplied to the said coil or coils, and after that the displaceable part of the core has taken the intended position in the working position of the device.

Aαx>rding to a further embodiment of the device in accordance with the invention hoisting and supporting means are arranged around the core or one of the poles or a stationary pole of the core for elevation of that object, which is to be heated or treated, from the table and/or a con¬ veyor which is arranged to the area for the poles of the core.

Further characteristics of, and advantages with the device in accordance with the invention will in the following description of the invention be apparent by eπbodiment examples, whereby a simultanεϊcus reference will be made to the acexmpanying schematic drawings, of which Fig. 1 shews from

one side a part of a device in accordance with the invention and accord¬ ing to one embodiment, Fig. 2 shows from above a frame, Fig. 3 shews from one side a part of a device in accordance with the invention and accord¬ ing to an another embodiment and Fig. 4 shews from one side a part of a table according to a second embodiment.

With the reference designation 1 in Fig. 1 and 3 is shown a part of a device which is intended for heating objects 11, 12, 13, derubberizing, shrink fit operation or an another work operation of a workpiece by uti- lization of elec±rσtechnical method or magnetic technique. The device 1 comprises in this respect a core 2 or a yoke, which is arranged to be able to close when necessary or in applicable cases, at least one coil 3, 4 or as it is evident from the figures two coils 3 and 4, which are arranged around the poles 5 and 6 of the core 2. It is further evident from the figures that there is a gap 7 between the poles 5, 6 of the core 2, which gap can be closed by the fact that the poles 4, 5 are brought to lie against each other with their end surfaces 10 or that an object 11, 12 is arranged between the poles 4, 5 or their end surfaces 10 and in that way bridges the gap 7 or short-circuit the core 2.

Thus, at least one of the poles 5 or 6 of the core 2 is arranged displa¬ ceable or, according to the embodiment examples, a part 8 of the core 2 is arranged displaceable by means of a piston 9 or cylinder, such as a pneumatically working cylinder.

The coil or coils 3, 4 are connected to an a.c. source 20 by means of wiring 21 to form primary windings for induction of a magnetic field, the flux of which is intended to follow the core 2 or the core and an object 11, 12 arranged between the poles 5, 6 of the core.

Objects 11, 12 with lew weight or smaller objects 11, which substantially can be hold within the end surfaces 10 of the poles 5, 6, can be placed directly on one of the poles 6 or its end surface 10 and vΛiich pole 6 can be a stationary arranged pole. More bulky or voluminous objects 12, 13 or objects with proportionately heavy weight are arranged on a table 14 com¬ prised in the device 1 and which table consists at least partly of elect¬ rical insulating material and can comprise a plate-shaped element of such insulating material. The table 14 or the plate-shaped element shows, according to one embodiment of the device 1, an opening 15 or a through

hole, through which the core 2, or acx»rding to the embodiment example, the stationary arranged pole 6 of the core 2 can extend. Preferably, the said opening 15 is arranged centrally in the table 14. On the table 14 or the plate-shaped element can wearing rails 16 or similar be arranged to prevent unnecessary wear on the table 14, the plate-shaped element or the insulating material. Further, the table 14 can be arranged vertically ad¬ justable, whereby the object 12, 13 i.a. can be placed on an appropriate level in the device for the heating or treatment of the object, attain a satisfactory connection to the poles 5, 6 and the core 2, avoid mechani- cal influence en at least one of the poles 6 or on the core 2. m one embodiment of the device 1 is a conveyor or similar arranged to the device and to the area for the poles 5, 6 of the core 2 to facilitate the supply of objects 11, 12, 13 to the device and when removing heated or treated objects. Such objects can consist of objects with heavy weight and or are bulky or in another way are difficult to handle. At this it is also an advantage and sometimes a necessity that the table 14 is arranged in such a way that it can be raised and lowered.

When heating or in treatment of objects 11, 12, 13, as when preheating moulding tools, the object or in applicable cases the objects are arrang¬ ed on the table 14 and on a suitable level in the device 1, whereby the poles 5, 6 of the core 2 are brought to lie against the object so that the core 2 will be closed and s ort-circuited. Smaller objects 11 or objects with lew weight can, as said, be arranged on the end surface 10 of one of the poles 6. Preheating can also take place for other kind of objects, which only to some extent consist of metal and the remaining part of polymeric material, such as rubber. In derubberizing, which is to separate polymeric material from metal inserts, one or more objects are placed on the table 14, whereby the objects are induced or arranged in the previous said and customary manner. When heating or in treatment of objects 13, which are in the form of a ring or similar, i.e. have a ^■ through or centrally opening, such an object 13 is arranged on a table 14 and in such position, that the core 2 or one of its poles 5, 6 or both poles can be brought to run through the said opening of the object. At this two parts 8 of the core 2 or both poles 5, 6 can be arranged displa¬ ceable. In this respect and according to one embodiment of the device 1 hoisting and supporting means can be arranged around the core 2 or one of the poles 5, 6 for elevation of the object 13 from the table 14 or a con¬ veyor, by means of which the ebject has been supplied to the device 1 or

the area for the poles 5, 6 of the core. The hoisting and supporting means, which can be formed of rod-shaped devices, pneumatic or hydraulic devices or such said devices operating in such a way, can, when utilizing of for example tables 14, be arranged to extend through the table and be displaceable from or beneath its surface or from or under the surface of existing wearing rails 16 and to a level above the table. The supporting surfaces of the hoisting and supporting means are provided with or con¬ sist of insulating material. Besides the function as hoisting and supp¬ orting means and positioning means for objects, it is, for example, atta- ined that heating losses are avoided to the foundation, especially if the foundation consists of a material with high thermal conductivity, etc., as metal, which is often used in wearing rails 16, conveyors and similar. When heating ring-shaped objects, for example wearing rings or wheel rims, there are, for example, four hoisting and supporting means arranged around the core for elevation of the ring. After this, the core 2 is brought to close, for example by the fact that one part 8, one of the poles 6 or the lower pole 6, is brought to displacement towards and against the other pole 5 and its end surface 10. The object 13, in the form of the ring, will at this form a secondary winding and be induced. The table 14 or the plate-shaped element of insulating material can in this case be replaced of a conveyor or similar. Heating or treatment of ring-shaped objects 13 can constitute a method for shrink fit, i.e. that the ring-shaped object is brought to heating and in that respect to thermal expansion a couple of millimeters. Then, for example, a rim is brou<ght into the expanded ring, whereby a cooling of the ring is perform¬ ed and the ring pinch around the rim. The heating of the object can be done in few minutes or about 10 minutes compared to four to six hours when using a conventional furnace and with an energy consumption of one third compared to conventional heating method.

To attain an inprσved contact between one or more displaceable parts 8 of the core 2 and the core for the rest, the device 1 comprises, according to one embodiment, a press device 17, see for example Fig. 1. The press device 17, for example in the form of a pressure box device, is arranged to press the displaceable part 8 of the core 2 against the core and reduce or eliminate the joint 16 between the core 2 and the said part 8 or said parts. Thus, the displaceable part 8 of the core 2 is brought to take the intended position in the working position of the device 1 by means of an influencing device 9, such as a pneumatic cylinder. Then the

press device 17 is brought to press the displaceable part 8 against the core 2. After that a magnetic flux can be permitted through the core 2. In an another device, which was lacking of a press device 17, ^■ there was never obtained a surface contact or an invariable surface contact between the displaceable part 8 and the core 2. The magnetic flux or magnetic field caused the displaceable part 8 to vibrate during the working opera¬ tion or during the closing of the circuit with the current source 20.

The displacement of the press device 17 is shewn in Fig. 1 with the refe- rence designation 18 and the displacement of the displaceable part 8 of the core 2 is shown by the arrow 19.

With a further reference to Fig. 2, it is shown a frame 22 in the table 14 or a supporting frame for the said plate-shaped element of for the insulating material. The supporting frame 22 is at least to a considera¬ ble extent shaped of a durable material, as customary structural material as metal, for example in form of a sheet profile. Such a frame 22 and especially if it forms a closed frame, i.e. without breakage or similar, will, when used in a device 1 acx»rding to the invention, form a winding or a secondary winding and be induced. The supporting frame 22 according to the invention and the embodiment example shewn in Fig. 2 is shaped partly of a first material 23 and according to the example a sheet pro¬ file, which is divided in such a way that a portion is lacking and forms an opening 24, a gap, an interruption or similar and thus shews end port- ions 27 located at a distance from each other, partly a second material 26, which in shape of a frame piece 25 is designed to close, overlap or restore the supporting frame 22. Said second material consists of elect¬ rical insulating material, such as glass fibre reinforced plastic, for example polyester, bakelite or another composition of pheneplastic or another rigid and non-conductive material.

Furthermore, the core 2 can be constructed by sheet bars, which CU connected to each other to form a body, rod or similar, and shall compose the core 2. As connecting medium can be used a glue or a varnish, such as an insulating varnish based on rosin oil, polyamide or epoxy resin, while the sheet bars can be made of sheets of silicon carbide.

In Fig. 3 is shewn a second embodiment of a device 1 accoπiing to the invention and having a table 14, which is arranged beside the core 2 and

is arranged displaceable towards the core 2 and at a level below the poles 5, 6 of the core 2 in order to be able to supply objects 12, 13 for heating or treatment into the gap 7 between the poles and also be able to be displaced to pass or essentially pass the poles. At this the table 14 can be provided with objects 12, 13 and the objects are moved into the gap 7 for heating or treatment. The rest of the device 1 can be in accor¬ dance with or substantially in accordance with the previously shown and described device and the reference designations designate corresponding parts of the device according to the previous device.

With further reference to Fig. 4 it is shown an embodiment example of a table 14, which is arranged displaceable and provided with objects 12 for heating and treatment by the device 1. The table 14 is displaced, for example in the direction shewn by the arrow 28, for supplying the objects 12 to the device and according to the embodiment example shewn, the table has been moved so far into the device 1, that one of the objects 12 or the first object is located in front of the core 2 and into its gap 7 or in front of the poles 5, 6 of the core 2. Thus, it is shewn a core in section by the reference designation 2. When the treatment of the first object is finished, the table 14 is displaced an additional distance in the direction of the arrow 28 so that the second object 12 takes the intended position in the device 1, i.e. similarity to the position for the first object shewn in Fig. 4. After that the treatment of also the second object 12 has been carried out, the table 14 can be arranged to return or for further displacement in the direction of the arrow 28, whereby the objects 12 are unloaded on the opposite side of the device l.

When using a device 1 in accordance with the invention one attains beside short heating times to a low cost also low maintenance costs, as the de- vice is simple in its construction and has few movable parts. Further, an uniform quality can be maintained in manufacture and an effective control and adjusting of the process can be carried out. In, for example, prehea¬ ting moulding tools, it is gained shorter set-up times when using a devi¬ ce 1 in accordance with the invention and one gets an optimum of utiliza- tiαn of moulding presses and similar machines. When derubberizing, the metal part of the product can be re-used. Furthermore, a use of the devi¬ ce 1 results in an improved working environment, as the process is clean and only the objects, which shall be heated, are heated, i.e. not the surroundings. Tools in a maehsie or press can be exchanged at short notice

In a test a tool unit, comprising a tool with a ring and a bed with a weight of nearly 200 kilos, was heated to 450° C in 15 minutes. A corre¬ sponding heating in a hot blast furnace consumes a time of four to six hours.

Without exceeding the scope of the concept of the invention, modifica¬ tions of the device should be possible. Thus, there are treatment cases where it is not necessary and sometimes not possible to close the core, whereby the device in accordance with the invention yet can be used in an intended way and with an absolute satisfactory effect. The core or its poles can be stationary in certain particular cases of treatment, while in other cases one of the poles or both poles are arranged displaceable. Instead of a table around the core or its poles or one of the poles a conveyor or one end part of a conveyor can be arranged, whereby a preva- lent conveyor with rollers of metal can be used. At this a hoist is arranged beneath the conveyor or around the core to hoist that object from the conveyor, which is to be treated. A table consisting of an insu¬ lating material can be provided with wearing rails of metal to resist the wear. Further, the table can be arranged stationary even if advantages are attained when the table is vertically adjustable. A displaceable table, which is located beside the poles of the core and is movable in a direction below the poles of the core, can show an extensiveness and design for supporting more or a number of objects and objects with a shaping making the objects difficult to place. When the device will be used for shrink fit operations hoists and stores can be arranged in connection with the device for hoisting and storing such parts, which are to be fitted to the heated part for the joining of such parts by means of shrink fit. It is not excluded to arrange a coil or a coil which is removable from the gap between the poles of the core, as it is in many cases the best location of a coil. In known devices with a coil placed in said manner prevent the supplying of work pieces or objects for heating and treatment to the space between the poles of the core. Ey arranging such a coil removable said inconvenience is eliminated. In this respect it should also be possible to arrange the coil exchangeable with other coils showing other dimensions or diameters, whereby an adaption of the device can be performed for heating or treatment of objects with widely separated dimensions and shaping. At the same time a more effective con¬ trol of the process can be carried out in certain special cases. Further¬ more, more coils can be used in the device than what has been mentioned

previously. The device in accordance with the invention is thus not re¬ stricted to what has been described and shown in the embodiment examples but solely by the following claims.