Method of Disassembling Resin-Molded Equipment

In the accompanying drawings

FIG. 1 is a schematic illustration of facilities for executing the method of one embodiment of the invention;

FIG. 2 is a schematic perspective view, partially broken, of the major part of the facilities in FIG. 1;

FIG. 3 is a graph showing the relationship between the temperature of a sample piece and the decomposition rate of the sample piece caused by a ray fungus;

FIG. 4 is a schematic illustration of facilities for executing the method of a second embodiment of the invention; and

FIG. 5 is a view similar to FIG. 4 showing a third embodiment of the invention.

A first embodiment wherein a transformer comprising a resin-molded coil assembly is to be disassembled will now be described with reference to FIGS. 1 to 3 of the accompanying drawings. A microorganism and more specifically, Nocardia in the order of ray fungi is employed for forming a gap in the method of the first embodiment, as will be described in detail later. The ray fungus releases oxygen such that the carbonic double bond of epoxy resin molecules is severed and the oxygen is linked to the carbon atoms. FIG. 3 illustrates the relationship between the temperature of a sample piece and the decomposition rate decomposition rate of the sample piece caused by a ray fungus. As shown in FIG. 3, the decomposition rate of the ray fungus is relatively high at an ambient temperature of approximately 35.degree. C., i.e. or the ray fungus is relatively active at the ambient temperature of approximately 35.degree. C. When the net weight of the material decomposed at 35.degree. C. is considered as 100%, the ray fungus has characteristics such that the decomposition rate thereof is decreased to 90% at 20.degree. C. and to 77% at 10.degree. C. When the ambient temperature is further decreased, the ray fungus becomes still less active. The ray fungus also becomes less active when the ambient temperature is increased to 50.degree. C. or above. The ray fungus is killed when the ambient temperature is increased to 60.degree. C. or above.

Referring to FIGS. 1 and 2, reference numeral 11 designates a housing defining a processing compartment 12 filled with air or oxygen. The processing compartment 12 may be formed by partitioning a working space of a building. The building may be furnished with air conditioning system so that the indoor air is cooled. Alternatively, an industrial or household refrigerator may be employed for providing the processing compartment 12. The ambient temperature of a resin-molded coil assembly 2 or other resin-molded equipment is set to a temperature between 0.degree. and 10.degree. C. The resin-molded coil assembly 2 comprises a cylindrical low-voltage coil 3, a cylindrical high-voltage coil 4 disposed outside the low-voltage coil 3, and a resin layer 5 molded from resin for enclosing the coils 3 and 4 together. A power supply circuit 13 with an output adjusting function is connected to terminals 6 of the coil 4 of the resin-molded coil assembly 2. The resin layer 5 of the molded coil assembly 2 has a hole formed in the portion thereof in the vicinity of the coil 4 by means of drilling. A temperature sensor 15 is inserted in the hole 14. A resistance measurement device 16 is connected to the terminals 6 of the winding 4. The power supply circuit 13 is adapted to feed an electric current to the coil 4 so that the coil 4 generates heat. The output of the power supply circuit 13 or the output voltage thereof is controlled so that the temperature of a boundary portion between the resin layer 5 and coil 4 reaches approximately 35.degree. C. More specifically, the power supply circuit 13 is adapted to control the output voltage based on a temperature signal obtained based on the resistance value measured by the resistance measurement device 16, whereby the temperature of the coil 4 heating is controlled to be approximately 35.degree. C. A temperature sensor 15 is provided for sensing the temperature of the resin layer 5, thereby producing a control signal. The control signal is supplied to the power supply circuit 13 or the air conditioner which controls the temperature of the resin layer so that the temperature of the resin layer is usually maintained at temperature lower than that of the coil 4. Such control of the temperature of the resin layer 5 is made in order that the ray fungi act concentrically on the boundary portion between the coil 4 and the resin layer 5.

The ray fungi are attached to the terminals 6 of the coil 4 and the temperature of the boundary portion between the resin layer 5 and the coil 4 is maintained at approximately 35.degree. C. Since the ambient temperature of the molded coil assembly 2 ranges between 0.degree. and 10.degree. C. and the temperature of the boundary portion is maintained at approximately 35.degree. C., the ray fungi gather to the boundary portion and become active there. The ray fungi go inward with the boundary portion oxidized to be decomposed. It takes about two months to decompose 3 to 4% of the molded coil assembly 2 from the outer surface thereof when the entire coil assembly 2 is maintained at the temperature of approximately 35.degree. C. However, when the temperature of the portion of the coil assembly 2 in the vicinity of the coil 4 is concentrically controlled to be approximately 35.degree. C., the portion of the coil assembly 2 in the vicinity of the coil 4 may be concentrically decomposed by the ray fungi, whereby the bond between the coil 4 and the resin layer 5 may be rapidly released. Consequently, a gap is formed in the boundary portion of the coil 4 and the resin layer 5. The gap may or may not completely separate the coil 4 from the resin layer 5. Even when the gap thus formed does not cover all of the boundary portion between the coil 4 and the resin layer 5, the coil 4 may be separated from the by resin layer 5 with ease by the application of a relatively small external drawing or pushing force to the coil 4 since the gap formed serves to reduce the bonding strength between the coil 4 and the resin layer 5. Thereafter, the coil 4 is pulled out and recycled.

The resin layer 5 may or may not be broken into pieces so as to be employed for reclamation or as building materials. Alternatively, the resin layer 5 may be continuously decomposed by the ray fungi even after the separation from the coil 4 with the temperature thereof maintained at approximately 35.degree. C. The resin layer 5 is finally decomposed to carbon dioxide and water, which may be collected to be recycled for plant cultivation at farms or the like. Since the ray fungi become less active in the temperature range between -10.degree. and 0.degree. C, the ray fungi may be preserved in a glass vessel or the like in that temperature range. Additionally, the low-voltage coil 3 may be separated from the resin layer 5 in the same manner as described above

According to the foregoing embodiment, the gap is formed in the boundary portion between each of the coils 3, 4 and the resin layer 5 and thereafter the coils 3, 4 are separated from the resin layer 5. Thus, the coils 3, 4 may be separated from the resin layer 5 with ease and collected so as to be recycled. Furthermore, organic substances of the resin layer 5 may be decomposed without resin dust produced during the disassembling.

Although the ray fungus is employed as the microorganism in the foregoing embodiment, other microorganisms acting in the same manner as described above may be employed. Although both of the temperature sensor 15 and the resistance measurement device 16 are employed for controlling the temperature of the boundary portion between the coils and the resin layer, either one of them may be employed for sensing the temperature of the portion of the coil assembly in the vicinity of the coils. Furthermore, when the outdoor temperature is below 10.degree. C., the processing compartment 12 may or may not be provided. Additionally, in the case where the molded transformer is split owing to an accident during operation with the windings cut off and cut winding ends are exposed from the split portion, the transformer may be separated from the resin layer in the above-described manner when an electric current can be caused to flow into the cut winding ends from the outside.

A second embodiment of the invention will now be described with reference to FIG. 4. In this embodiment, a resin-molded bushing 21 is adopted as the resin-molded equipment. The resin-molded bushing 21 is disassembled by making use of a difference in thermal expansion, as will be hereinafter described in detail. The resin-molded bushing 21 has a round bar like central conductor 22 covered with resin-molded material. Reference numeral 23 designates the resin layer. An electromagnetic induction heating apparatus 24 is provided around the resin-molded bushing 21 for heating the central conductor 22. As is well known in the art, the electromagnetic induction heating apparatus 24 comprises an induction coil 25 and a high frequency power supply 26 supplying a high frequency current to the induction coil 25. An electromagnetic field provided by the induction coil 25 causes an induction current in the central conductor 22. The Joule's heat generated by the induction current causes the central conductor 22 to self-heat. The temperature of the central conductor 22 is sensed by a temperature sensor 27. Based on the sensed temperature, control means 28 controls the amount of high frequency current supplied to the central conductor 22 from the high frequency power supply 26.

When the central conductor 22 is heated, the difference of thermal expansion between the central conductor 22 as a metallic body and the resin layer 23 causes a tearing force between them. For example, the thermal expansion coefficient of copper is 20.times.10.sup.-6 /.degree. C. and that of epoxy resin is 180.times.10.sup.-6 /.degree. C. Thus, a gap is gradually formed in the boundary portion between the central conductor 22 and the resin layer 23. After a sufficient gap is formed, the central conductor 22 is separated from the resin layer 23 and pulled out to be recycled. The resin layer 23 may or may not be broken into pieces so as to be employed for reclamation or as building materials.

The same effect as in the first embodiment is achieved in the second embodiment. In particular, the disassembling work may be performed in a relatively short period in accordance with the method of the second embodiment.

Although the central conductor 22 is induction heated by the induction heating apparatus 21 in the second embodiment, a low frequency current or DC current may be directly supplied to the central conductor 22 so that the conductor 22 is caused to self-heat.

FIG. 5 shows a third embodiment. In the case of disassembling the resin-molded bushing 21 by making use of the difference of thermal expansion, the resin layer may be heated by a dielectric heating of apparatus instead of the metallic body, as shown in FIG. 5. An electrode 29 having less than one turn is provided around the resin layer 23 of the bushing 21. A high frequency voltage from the high frequency power supply 26 is applied across the electrode 29 and the central conductor 22. Consequently, heat resulting from dielectric loss is applied to the resin layer 23. The difference of thermal expansion between the central conductor 22 and the resin layer 23 causes a gap in the boundary portion therebetween. The same effect as in the first embodiment may thus be achieved in the third embodiment.

The foregoing disclosure and drawings are merely illustrative of the principles of the present invention and are not to be interpreted in a limiting sense. The only limitation is to be determined from the scope of the appended claims.