CA1321736C - Process for forming one or more insulated films on the surface of a solid body and an apparatus therefor - Google Patents
Process for forming one or more insulated films on the surface of a solid body and an apparatus thereforInfo
- Publication number
- CA1321736C CA1321736C CA000558880A CA558880A CA1321736C CA 1321736 C CA1321736 C CA 1321736C CA 000558880 A CA000558880 A CA 000558880A CA 558880 A CA558880 A CA 558880A CA 1321736 C CA1321736 C CA 1321736C
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- Prior art keywords
- solid body
- insulated films
- insulated
- solid
- films
- Prior art date
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/04—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing coils
- H01F41/12—Insulating of windings
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Insulating Of Coils (AREA)
- Manufacture Of Motors, Generators (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention relates to a process for forming one or more insulated films on the surface of a solid body comprising pressing towards said solid body one or more insulated films which are so arranged as to cover at least a part of said solid body and are impregnated with a resin and at the same time curing said impregnated resin, characterized in that on curing said impregnated resin while pressing said one or more insulated films a large number of solid particle bodies are densely provided on the external surface of said one or more insulated films, said one or more insulated films are pressed onto the surface of the solid body through said solid particle bodies and the impregnated resin is cured in that state and an apparatus therefor.
According to the present invention, there can be obtained one or more insulated films having a uniform thickness as a whole and no remaining air and excellent in adhesion.
The present invention relates to a process for forming one or more insulated films on the surface of a solid body comprising pressing towards said solid body one or more insulated films which are so arranged as to cover at least a part of said solid body and are impregnated with a resin and at the same time curing said impregnated resin, characterized in that on curing said impregnated resin while pressing said one or more insulated films a large number of solid particle bodies are densely provided on the external surface of said one or more insulated films, said one or more insulated films are pressed onto the surface of the solid body through said solid particle bodies and the impregnated resin is cured in that state and an apparatus therefor.
According to the present invention, there can be obtained one or more insulated films having a uniform thickness as a whole and no remaining air and excellent in adhesion.
Description
11 32~73~
(FIELD OF TH~ INVENTION) The present invention relates to an improvement of a process for forming one or more insulated films on the surface of a solid body such as an insulatlng coil or a grip of a cutting pliers.
(DESCRIPTION OF THE PRIOR ART) The present invention may be applied to any articles or parts on which one or more insulated films are coated an~ will be explained with reference to the insulated conductor wherein an insulating film is coated on a conductor.
Generally as the method for formir.g one or more insulated films which will be covered on a bared conductor, there are mentioned a variety of methods such as coating an insulating paint on the surface of a conductor, covering one or more insulated films, which ha~e been previously formed in a cylindrical shape (or a bag shape) over a conductor, winding an insulating tape (or sheet) around a conductor to form one or more insulated films on the surface of the conductor and the like. Usually these methods are appropriately selected and adopted depending on specific forms of the articles or parts.
-- 1 -- *
~ 32:~73~
1 The present invention relates to the last method among the above-mentioned ones, that is, a method for forming one or more insulated films by winding an insulating tape (or an insulating sheet) around a conductor to form one or more insulated films.
The method for forming one or more insulated films by winding an insulating tape, as disclosed also in Japanese Patent Application Kokai (Laid-Open) No.
49455/77, is usually conducted by winding a certain kind of an insulating tape around a conductor so as the part of the tape to overlap, subjecting the tape to resin impregnation (or winding the tape on which a resin has previously coated around a conductor) and curing the resin on the tape at the state by putting external force through a plate on the external surface (or heat-curing in the case of a thermosetting resin).
The method has almost no problem for forming one or more insulated films used for popular applications, but when it is adopted for forming the ones which may be exposed to vigorous vibration or impact or on which electrically excessive voltage or impulse voltage is apt to be applied, the films tend to be weakened mechanically or electrically. In other words, the one or more insulated films having been cured by applying external force to a plane through a plate seem apparently to be formed uniformly in thickness because of the flatness of the external surface. However, the conductor itself has warpage or deformation~ to some extent, so - 2 - ~
132173~
1 that the one or more insulated films may be pressed unevenly by the pressure of the plate, that is to say, adhesion between the conductor and the one or more insulated films will not be uniform thus happening peeling at the parts to which pressing force is applied only weakly. Furthermore, the corner parts or curve forming parts are at the worst in view of the adhesion, and voids are likely to be formed and electrical proper-ties are degraded at these parts where pressing force is applied weakly.
In order to improve this point there has recently been proposed a method for forming one or more films, in which an insulating film (or tape) having been wound around a conductor and subjected to resin impregnation, of which the whole external surface having been subjected to fluid sealing, is dipped into an insulating oil in a sealed container and heat-cured with pressure by raising the pressure and temperature of the insulating oil.
The method presses uniformly the whole surface of the one or more insulated films regardless of the presence of the deformation, corner parts or curved parts of the conductor, that is to say presses the surface without any unevenness of the pressing force and thus the adhesion is largely improved as compared with the above-mentioned. However, as a result of our detailed experiments, it was found that this method for forming the one or more films has also the following ~ 32~73~
1 problems:
This method is conducted in oil, and thus whole of the one or more insulated films placed on the surface of a solid body is uniformly pressed. However, air between the conductor and the film or within the film layer will remains at the part in a compressed state, so that the one or more insulated films cannot exhibit satisfactorily the electrical properties which are possessed intrinsically by the film. Moreover, during operation or using of the products insulated by this method, for a long time peeling is apt to be caused by the remaining of the compressed air and thus the film becomes weakened mechanically.
Thus, it is impossible to remove the air remaining within the layer of insulating film, because this method is conducted in compressed oil and the air remains within layer of insulating film in a compres-sed state.
SUMMARY OF THE INVENTION
~0 The present invention is conducted in view of the above reason and the object of the present invention is to provide a method for forming one or more insulated films on a conductor (solid body) having a uniform thickness and an excellent adhesion wherein no air will remain between the conductor and the film or within a film layer even if the conductor has warpage, deformation or curved parts and a'l parts of the film are pressed 132~73~
uniformly irrespective of the warpage, deformation or curved parts of the conductor.
In other words, the present invention is a method for accomplishing the expected object on curing the impregnated resin in the above-mentioned film while pressing the one or more films by providing densely a large number of solid particle ~odies on the external surface of the one or more insulated films, pressing the one or more insulated films onto the surfaced of the solid body through the solid particle bodies and curing the impregnated resin in that state.
~ ccording to this method, whole of the one or more insulated films provided on the surface of the solid body is uniformly pressed by a large number of solid particle bodies provided on that external surface, the air between the insulated film and the solid body and within the insulated film layer is expelled through the space between the solid particle bodies to the exterior of the layer in a state in which whole of the one or more ~0 insulated films are uniformly pressed and the impregnated resin is cured in the state that the air is expelled, so that the one or more insulated films formed on the surface of the solid body will be the one which has a uniform thickness and no remaining air therein and is excellent in adhesion.
132~73~
According to one aspect of the invention there is provided a process for forming one or more insulated films on the surface of a solid body comprising pressing towards said solid body one or more insulated films which are so arranged as to cover at least a part of said solid body and are impregnated with a resin and at the same time curing said impregnated resin, characterized in that on curing said impregnated resin while pressing said one or more insulated films a large number of solid particle bodies are densely provided on the external surface o~ said one or more insulated films, said or more insulated films are pressed onto the surface o~ the solid body through said solid particle bodies and the impregnated resin is cured in that state.
In accordance with another aspect of the invention there is provided an apparatus for forming one or more insulated films on the surface of a solid body comprising pressing to the solid body one or more insulated.
films which are so arranged as to cover at least a part oP
~0 the solid body and are impregnated with a resin and at the same time heat-curing said impregnated resin, characterized in that a container Por receiving said solid body which is covered with said one or more insulated films, said particle bodies which are put in said container and in 5a A
.. ` ` .. .. . . ~ . .
` ``." :. - `. : `
.
.
132173fi which said solid body has been embedded and a pressing means îor applying pressing force to said solid particle bodies are provided, so that the pressing force by said pressing means is applied to sai~ one or more insulated films through said solid particle bodies.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a vertical section o:E an apparatus 5b ~32~ 736 l for forming one or more insulated films of the present invention in order to illustrate an example of a process for forming the one or more insulated films of the present invention, Fig. 2 is a vertical section which illustrates only a container of Fig. l, Figs. 3 - 5 illustrate the examples of the process of the present invention sequentially, in which Fig. 3 illustrates a perspective view of the insulated conductor and Figs. 4 and 5 illustrate vertical sections of the apparatuses, Fig. 6 is a vertical section of the appara*us for illustrating another example of the process of the present invention, Fig. 7 shows tan ~ - voltage characteristics of the one or more insulated f ilms, and Fig. 8 is a partly broken perspective view of the insulating coil.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is explained in detail with reference to the following examples.
E`igs. 3 and 4 illustrate the process for forming the one or more insulated films of the present invention sequentially.
These figures illustrate the case of forming the one or more insulated films on the insulated connect-ing conductor which is usually used for electric coupling ~321736 1 of the electric apparatuses at a power station or a transforming station. First of all, as shown in Fig. 3, an insulating tape 3 coated with a resin is wound around a conductor 2 with overlapping a part of the tape to form an expected film layer 4 on the surface of the conductor 2. If a tape on which no resin is coated is used, the film layer is subjected to resin impregnation after winding the tape. The resin is generally impregnated by vacuum pressure impregnation.
Next, the film layer 4 is molded by pressing in a non-cured state of the impregnated resin, in which the molding by pressing is conducted in the solid particle bodies 5 as shown in Figs. 4 and 5.
That is to say, the insulated connecting conductor 1 is embedded into solid particle bodies 5 such as sand or iron balls contained in a container 6 (Fig. 4), and these solid particle body, as shown in Fig. 5, is pressed by a pressing means such as an oil pressure piston 7 or the like. The sign 8 provided right below the container 6 in the figure represents an air ventilating apparatus, and the sign 9 represents a filter for preventing the solid particle bodies 5 ~rom expelling out of the container through the air ventilating apparatus 8.
As mentioned above, to press the solid particle bodies embedding the insulated connecting conductor 1 with the pressing means 7 means to apply external force to the film layer 4 of the insulated connecting conductor 132~736 1 through the solid particle bodies 5. As the external force is applied just through the particle bodies, it is applied uniformly to all over the surface at fine intervals, that is, pressing force is uniformly added irrespective of the warpage or deformation of the solid body (i.e. conductor 2 in this case). At the same time, as the film is pressed through the particle bodies, air within the film layer 4 is expelled from the layer through the space between neighbouring particles, and the air thus expelled or the air pressure caused by the reduction of the container volume due to the movement of the pressing means is expelled externally through the air ventilating apparatus 8.
Accordingly, whole surface of the film layer 4 of the insulated connecting conductor (including corner parts and plain parts) is pressed uniformly by a predetermined pressure and the air existing within the layer is expelled sufficiently to the external direction, the contact surface of the film layer 4 and the conductor 2 and the interior of the film layer becomes the satisfactorily closely adhered state and the thickness of the film layer 4 itself becomes even. Finally the film layer is heat-cured for a predetermined time to give an insulated connecting conductor having an ideal insulation layer.
In the above explanation, pressing of the one or more insulated films through the solid particle bodies is illustrated with reference to an example. However, ~3217~
1 for practical application there may be created a variety of methods other than the above on consideration of the kinds of resin, methods for ventilating air, methods for pressing and the like.
Fig. 1 shows another example. In this example, there may be obtained a stronger adhesion as compared with the above-mentioned example, and elec~ric properties may be improved by applying the process to ~he insulated coil and the like. First of all, referring to circum-ferential apparatuses thereof and then to the process, there is a container 6 placed on a truck 10, in which container a heat resistant solid particle bodies 5 and an insulated coil la having previously been subjected to resin impregnation are contained. Particularly, the container is so formed as for a part of its wall to be deformable. In other words, in this example there is provided a heat resistant extensible member 11 such as a polyester film wall at the upper part of the container 6. On the side wall of the container 6, there is also provided a piping 12 for producing vacuum within the container, which piping is connected to an external pressure reducing means such as a vacuum pump 15 through a flexible pipe 13 and a valve 14.
Moreover, the container 6 is arranged together with the truck 10 within a heating oven. Within the heating oven 16 a heating apparatus 17 is provided for drying the inside of the heating oven.
Main apparatuses being as mentioned above, it _ g _ 132~73~
1 is important that not only the extensible member 11 provided at the upper part of the container 6 has a strength for preventing itself from being broken when the container has been made vacuum by a vacuum pump, but also it can be deformed so that the solid particle bodies 5 are pressed satisfactorily at a certain level of vacuum, in other words, a means for pressing the solid particle bodies must have a construction that the container 6 is made vacuum and thus the solid particle bodies are pressed by the deformation of the extensible member (see Fig. 2), so that when the extensible member is deformed it physically contacts and presses the solid particle bodies. Therefore, it is desirable for the solid particle bodies 5 to be charged as much as possible in the container 6, because the deformation degree of the extensible member 11 may be little.
A process for forming one or more films of an insulated coil by using the apparatus is now explained.
The figure shows the state of the container 6 within which the insulated coil la is arranged. The process is explained starting from preceeding processes without illustration in figures. First of all, a coil is made by winding a conductor and formed and then a tape such as grass backed mica tape which has been impregnated with an epoxy type semi-cured thermosetting resin is wound around the coil to form an insulated coil la.
~ 32~L73~
1 Next, the insulated coil la is placed into the container 6, wherein the insulated coil is embedded deeply into the solid particle bodies 5 to ensure that the insulated coil will not be exposed from the solid particle bodies.
In this case, the extensible member 11 serves as a closure of the container and thus the extensible member 11 must be attached by providing a sufficient sealing to ensure isolation of the inside of the container from the outside after the insulated coil has been inserted into the container.
Then the insulated coil is placed in the heating oven 16 together with a container by a truck.
If the insulated coil la is so small in siz.e that an operator can easily carry it by hand, the container 6 may be previously arranged within the heating oven 16 within which the insulated coil la is accommodated in the container.
Next, if a vacuum pump 15 is operated to reduce a reduced pressure within the container 6, the extensible member 11 is deformed as shown in Fig. 2, that is, atmospheric pressure P is applied to the external side of the extensive member and the solid particles receives the pressing force by the extensive member, so that whole surface of the layer of the insulating tape on the insulated coil is uniformly pressed in the same way as in the aforementioned example to improve the unlformity of the thickness and adhesion.
', .
~32~736 1 Then, under this condition, the insulated coil is heated and cured in the oven.
Particularly in case that the process for forming a film conducted in this way is employed, not only the same effect as the above-mentioned one is generated since the process is also the pressing and heating of the insulating film by solid particle bodies as mentioned in the above example, but also air remaining within the insulated coil is enforcedly drawn out of the film simultaneously with the pressing of the solid particles as the pressing means employs the deformation of a container by vacuum within the container, that is, voids are reduced and thus adhesion may be further improved than in the above-mentioned example.
Fig. 6 shows a further example.
Pressing force is obtained by reducing pressure (making a vacuum) within the container also in this case, and explanation will be conducted only referring to the different points from the above. There is a tightly closed container 6, which is divided into two rooms Rl and R2 up and down by the extensible member.
In the lower room R2, the solid particle bodies 5 and the insulated coil la are received, and reduced pressure is produced b~ a vacuum pump 15. On the other hand, the upper room Rl is connected with a vacuum pump or pressurizing pump 15a. Cooperation of the pressurizing pump 15a and the vacuum pump 15 in the lower room makes possible to press further stronger the solid particle ~32173~
1 bodies 5. Particularly if it is intended to make the inside of lower room Rl extremely lower vacuum condition and at the same time to retain the pressing force in a relatively low level, pressure in the lower room is reduced vigorously and a vacuum pump is connected also to the upper room to reduce a pressure so as to obtain the pressing force from the difference of the two reduced pressures. Thus it will be possible to control freely the degree of vacuum and the pressing force.
The present invention having been explained with reference to the several examples above, there ma~v also be used as the pressing means the expanding force of a heat expanding body by the use of the heat on heating a resin, the weight of the solid particle bodies or the combination thereof. There may be also considered a variety o~ methods such as compulsively pushing a number of the solid particle bodies into a tightly closed container having a predetermined volume or the like.
As the solid particles, those having a particle diameter of 10 - 800 ~ are optimal, and sand such as molding sand is most inexpensive and practical. It will be possible to employ any other particles such as metal balls, glass beads or the like which form space between the adjacent ones and retain air permeability on gathering together.
Having explained for the case of parts wherein one or more insulated films are formed on the surface ~ 32~73~
1 of a solid body and the one or more insulated films and the solid body are integrally used, the present invention is also applicable to the case of producing an insulating plate or insulating molded article by the use of a molding tool. That ls to say, when the insulating plate having a wave shape is intended to be produced, an insulating film having been impregnated with a resin is placed on the solid body having a wave-shaped surface and pressed in the solid particle bodies in the same manner as the aforementioned examples.
In this case, as the solid body and the insulating film are finally to be separated, it is needless ~o say that a release agent is preliminarily provided between the solid body and the insulating film. Insulating molded articles produced according to the process have no void in their layers and thus form a dense layer as those mentioned above, and it is also possible to obtain a layer having a uniform thickness along the shape of the surface of a solid body.
Next, one or more insulated films produced by the process of the present invention and the one produced by the conventional process are compared from the viewpoint of their effects.
Furthermore, it is difficult to evaluate the insulated coils produced by these processes from the viewpoint of their mechanical effects, that is, the degree of peeling and the results cannot be expressed specifically herein. However, it is well-known in the 11 3217~
l art that fewer voids in the insulating layer and uniform thickness of the insulating film over the whole surface will exhibit excellent properties in the insulated coil.
Fig. 7 is a test results of the insulated coil formed by the process of the present invention from the viewpoint of electri.c property which will be largely effected by the presence of void and shows the relationship between test voltage and tan ~ (%).
The insulated coil tested is a commutating-pole coil used for a direct current traction motor for a car (see Fig. 8), which has an oval shape with a total length of 320 mm and a total width of 100 mm, a rectangular section of 60 x 32 mm and a rated voltage of 400 V.
lS In Fig. 7, the curve X represented by a dotted line shows the test result of an insulated coil produced by the conventional process for forming a film, briefly saying, the one formed by pressing through a plate on the external side of the one or more films, wherein as i9 apparent from the figure tan ~ sharply increases at the test voltage higher than 2.5 kV.
The curve represented by a chain line y shows the result o~ an insulated coil produced by curing by applying oil pressure in an insulated oil, wherein tan ~, fluctuating little to the test voltage, is wholly in a higher level. On the other hand, the curve Z represented by a solid line shows a result of an insulated coil produced by the process of the present invention, wherein .
7 3 ~
1 as is apparent from the figure tan ~ remains wholly in a low level and will not increase largely.
Table 1 shows the results of measurement for evaluatin~ the uniformity of the insulation thickness of coils (see Fig. 8 with reference to the measuring point), wherein the thickness at the corner part t3 ~mean value) and those at the plain side parts t and t2 (mean value~ of the section of the insulated coil are particularly compared.
As is apparent from the result, there is no significant difference between the thicknesses at the plain parts in the coils formed by the conventional process and by the process of the present invention.
However, at the corner parts there is observed a remarkable improvement for the coil formed by the process of the present invention as compared with the one formed by pressing through a plate, and the coil produced by the process of the present invention has the same uniform thickness as in the coil produced by pressing in oil.
:~32~736 Table 1 _ Film formed by the .conventional processFilm formed by Measurlng the present pointthrough Pressing invention Interior1.5 mm 1.5 mm 1.5 mm gide (t2) L 1~4 1.5 l.S
part (t3) ~ 1.4 1.4 1 Table 2 shows the test result of dielectric breakdown voltages, which was carried out for four coils each.
Measurement were conducted by putting an aluminium foil as on electrode on the hollow part of Fig. 8, that is, the interior wall, and applying a voltage between the above electrode and a lead lb.
From the result, it will be apparent that the film formed by the process of the present invention can be resistant to a high voltage of about 10% higher than that applied to the one or more conventional films.
- 17 - :
~321~36 Table 2 Film formed by the conventional process _ Fllm formed by a plate Pressing the present ~... _ ._ .
18.0 19.0 21.5 Breakdown 18.0 20.0 22.0 voltage (kV) 19.0 20.0 22.0 19.0 21.0 23.0 Mean value 18.5 20.0 22.1 1 [EFFECTS OF THE INVENTION]
As mentioned above in detail, according to the present invention when an impregnated resin in an insulating film is cured while pressing the film a large number of solid particle bodies are densely provided on the external surface of the insulating film, the insulating film is pressed onto the surface of the solid body through the solid particle bodies and the impregnated resin is cured in that state. Therefore, the insulating film is uniformly pressed through the surrounding solid particle bodies irrespect1ve of the corner part, deformed part or curved part of the sol1d body, and air between the insulating film and the solid :
body and within the insulating film layer is expelled - 18 ~
~32:~36 1 out of the layer through the space between the solid particle bodies, so that one or more insulated films having a uniform thickness as a whole and no remaining air and excellent in adhesion can be obtained.
- 19 -:
(FIELD OF TH~ INVENTION) The present invention relates to an improvement of a process for forming one or more insulated films on the surface of a solid body such as an insulatlng coil or a grip of a cutting pliers.
(DESCRIPTION OF THE PRIOR ART) The present invention may be applied to any articles or parts on which one or more insulated films are coated an~ will be explained with reference to the insulated conductor wherein an insulating film is coated on a conductor.
Generally as the method for formir.g one or more insulated films which will be covered on a bared conductor, there are mentioned a variety of methods such as coating an insulating paint on the surface of a conductor, covering one or more insulated films, which ha~e been previously formed in a cylindrical shape (or a bag shape) over a conductor, winding an insulating tape (or sheet) around a conductor to form one or more insulated films on the surface of the conductor and the like. Usually these methods are appropriately selected and adopted depending on specific forms of the articles or parts.
-- 1 -- *
~ 32:~73~
1 The present invention relates to the last method among the above-mentioned ones, that is, a method for forming one or more insulated films by winding an insulating tape (or an insulating sheet) around a conductor to form one or more insulated films.
The method for forming one or more insulated films by winding an insulating tape, as disclosed also in Japanese Patent Application Kokai (Laid-Open) No.
49455/77, is usually conducted by winding a certain kind of an insulating tape around a conductor so as the part of the tape to overlap, subjecting the tape to resin impregnation (or winding the tape on which a resin has previously coated around a conductor) and curing the resin on the tape at the state by putting external force through a plate on the external surface (or heat-curing in the case of a thermosetting resin).
The method has almost no problem for forming one or more insulated films used for popular applications, but when it is adopted for forming the ones which may be exposed to vigorous vibration or impact or on which electrically excessive voltage or impulse voltage is apt to be applied, the films tend to be weakened mechanically or electrically. In other words, the one or more insulated films having been cured by applying external force to a plane through a plate seem apparently to be formed uniformly in thickness because of the flatness of the external surface. However, the conductor itself has warpage or deformation~ to some extent, so - 2 - ~
132173~
1 that the one or more insulated films may be pressed unevenly by the pressure of the plate, that is to say, adhesion between the conductor and the one or more insulated films will not be uniform thus happening peeling at the parts to which pressing force is applied only weakly. Furthermore, the corner parts or curve forming parts are at the worst in view of the adhesion, and voids are likely to be formed and electrical proper-ties are degraded at these parts where pressing force is applied weakly.
In order to improve this point there has recently been proposed a method for forming one or more films, in which an insulating film (or tape) having been wound around a conductor and subjected to resin impregnation, of which the whole external surface having been subjected to fluid sealing, is dipped into an insulating oil in a sealed container and heat-cured with pressure by raising the pressure and temperature of the insulating oil.
The method presses uniformly the whole surface of the one or more insulated films regardless of the presence of the deformation, corner parts or curved parts of the conductor, that is to say presses the surface without any unevenness of the pressing force and thus the adhesion is largely improved as compared with the above-mentioned. However, as a result of our detailed experiments, it was found that this method for forming the one or more films has also the following ~ 32~73~
1 problems:
This method is conducted in oil, and thus whole of the one or more insulated films placed on the surface of a solid body is uniformly pressed. However, air between the conductor and the film or within the film layer will remains at the part in a compressed state, so that the one or more insulated films cannot exhibit satisfactorily the electrical properties which are possessed intrinsically by the film. Moreover, during operation or using of the products insulated by this method, for a long time peeling is apt to be caused by the remaining of the compressed air and thus the film becomes weakened mechanically.
Thus, it is impossible to remove the air remaining within the layer of insulating film, because this method is conducted in compressed oil and the air remains within layer of insulating film in a compres-sed state.
SUMMARY OF THE INVENTION
~0 The present invention is conducted in view of the above reason and the object of the present invention is to provide a method for forming one or more insulated films on a conductor (solid body) having a uniform thickness and an excellent adhesion wherein no air will remain between the conductor and the film or within a film layer even if the conductor has warpage, deformation or curved parts and a'l parts of the film are pressed 132~73~
uniformly irrespective of the warpage, deformation or curved parts of the conductor.
In other words, the present invention is a method for accomplishing the expected object on curing the impregnated resin in the above-mentioned film while pressing the one or more films by providing densely a large number of solid particle ~odies on the external surface of the one or more insulated films, pressing the one or more insulated films onto the surfaced of the solid body through the solid particle bodies and curing the impregnated resin in that state.
~ ccording to this method, whole of the one or more insulated films provided on the surface of the solid body is uniformly pressed by a large number of solid particle bodies provided on that external surface, the air between the insulated film and the solid body and within the insulated film layer is expelled through the space between the solid particle bodies to the exterior of the layer in a state in which whole of the one or more ~0 insulated films are uniformly pressed and the impregnated resin is cured in the state that the air is expelled, so that the one or more insulated films formed on the surface of the solid body will be the one which has a uniform thickness and no remaining air therein and is excellent in adhesion.
132~73~
According to one aspect of the invention there is provided a process for forming one or more insulated films on the surface of a solid body comprising pressing towards said solid body one or more insulated films which are so arranged as to cover at least a part of said solid body and are impregnated with a resin and at the same time curing said impregnated resin, characterized in that on curing said impregnated resin while pressing said one or more insulated films a large number of solid particle bodies are densely provided on the external surface o~ said one or more insulated films, said or more insulated films are pressed onto the surface o~ the solid body through said solid particle bodies and the impregnated resin is cured in that state.
In accordance with another aspect of the invention there is provided an apparatus for forming one or more insulated films on the surface of a solid body comprising pressing to the solid body one or more insulated.
films which are so arranged as to cover at least a part oP
~0 the solid body and are impregnated with a resin and at the same time heat-curing said impregnated resin, characterized in that a container Por receiving said solid body which is covered with said one or more insulated films, said particle bodies which are put in said container and in 5a A
.. ` ` .. .. . . ~ . .
` ``." :. - `. : `
.
.
132173fi which said solid body has been embedded and a pressing means îor applying pressing force to said solid particle bodies are provided, so that the pressing force by said pressing means is applied to sai~ one or more insulated films through said solid particle bodies.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a vertical section o:E an apparatus 5b ~32~ 736 l for forming one or more insulated films of the present invention in order to illustrate an example of a process for forming the one or more insulated films of the present invention, Fig. 2 is a vertical section which illustrates only a container of Fig. l, Figs. 3 - 5 illustrate the examples of the process of the present invention sequentially, in which Fig. 3 illustrates a perspective view of the insulated conductor and Figs. 4 and 5 illustrate vertical sections of the apparatuses, Fig. 6 is a vertical section of the appara*us for illustrating another example of the process of the present invention, Fig. 7 shows tan ~ - voltage characteristics of the one or more insulated f ilms, and Fig. 8 is a partly broken perspective view of the insulating coil.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is explained in detail with reference to the following examples.
E`igs. 3 and 4 illustrate the process for forming the one or more insulated films of the present invention sequentially.
These figures illustrate the case of forming the one or more insulated films on the insulated connect-ing conductor which is usually used for electric coupling ~321736 1 of the electric apparatuses at a power station or a transforming station. First of all, as shown in Fig. 3, an insulating tape 3 coated with a resin is wound around a conductor 2 with overlapping a part of the tape to form an expected film layer 4 on the surface of the conductor 2. If a tape on which no resin is coated is used, the film layer is subjected to resin impregnation after winding the tape. The resin is generally impregnated by vacuum pressure impregnation.
Next, the film layer 4 is molded by pressing in a non-cured state of the impregnated resin, in which the molding by pressing is conducted in the solid particle bodies 5 as shown in Figs. 4 and 5.
That is to say, the insulated connecting conductor 1 is embedded into solid particle bodies 5 such as sand or iron balls contained in a container 6 (Fig. 4), and these solid particle body, as shown in Fig. 5, is pressed by a pressing means such as an oil pressure piston 7 or the like. The sign 8 provided right below the container 6 in the figure represents an air ventilating apparatus, and the sign 9 represents a filter for preventing the solid particle bodies 5 ~rom expelling out of the container through the air ventilating apparatus 8.
As mentioned above, to press the solid particle bodies embedding the insulated connecting conductor 1 with the pressing means 7 means to apply external force to the film layer 4 of the insulated connecting conductor 132~736 1 through the solid particle bodies 5. As the external force is applied just through the particle bodies, it is applied uniformly to all over the surface at fine intervals, that is, pressing force is uniformly added irrespective of the warpage or deformation of the solid body (i.e. conductor 2 in this case). At the same time, as the film is pressed through the particle bodies, air within the film layer 4 is expelled from the layer through the space between neighbouring particles, and the air thus expelled or the air pressure caused by the reduction of the container volume due to the movement of the pressing means is expelled externally through the air ventilating apparatus 8.
Accordingly, whole surface of the film layer 4 of the insulated connecting conductor (including corner parts and plain parts) is pressed uniformly by a predetermined pressure and the air existing within the layer is expelled sufficiently to the external direction, the contact surface of the film layer 4 and the conductor 2 and the interior of the film layer becomes the satisfactorily closely adhered state and the thickness of the film layer 4 itself becomes even. Finally the film layer is heat-cured for a predetermined time to give an insulated connecting conductor having an ideal insulation layer.
In the above explanation, pressing of the one or more insulated films through the solid particle bodies is illustrated with reference to an example. However, ~3217~
1 for practical application there may be created a variety of methods other than the above on consideration of the kinds of resin, methods for ventilating air, methods for pressing and the like.
Fig. 1 shows another example. In this example, there may be obtained a stronger adhesion as compared with the above-mentioned example, and elec~ric properties may be improved by applying the process to ~he insulated coil and the like. First of all, referring to circum-ferential apparatuses thereof and then to the process, there is a container 6 placed on a truck 10, in which container a heat resistant solid particle bodies 5 and an insulated coil la having previously been subjected to resin impregnation are contained. Particularly, the container is so formed as for a part of its wall to be deformable. In other words, in this example there is provided a heat resistant extensible member 11 such as a polyester film wall at the upper part of the container 6. On the side wall of the container 6, there is also provided a piping 12 for producing vacuum within the container, which piping is connected to an external pressure reducing means such as a vacuum pump 15 through a flexible pipe 13 and a valve 14.
Moreover, the container 6 is arranged together with the truck 10 within a heating oven. Within the heating oven 16 a heating apparatus 17 is provided for drying the inside of the heating oven.
Main apparatuses being as mentioned above, it _ g _ 132~73~
1 is important that not only the extensible member 11 provided at the upper part of the container 6 has a strength for preventing itself from being broken when the container has been made vacuum by a vacuum pump, but also it can be deformed so that the solid particle bodies 5 are pressed satisfactorily at a certain level of vacuum, in other words, a means for pressing the solid particle bodies must have a construction that the container 6 is made vacuum and thus the solid particle bodies are pressed by the deformation of the extensible member (see Fig. 2), so that when the extensible member is deformed it physically contacts and presses the solid particle bodies. Therefore, it is desirable for the solid particle bodies 5 to be charged as much as possible in the container 6, because the deformation degree of the extensible member 11 may be little.
A process for forming one or more films of an insulated coil by using the apparatus is now explained.
The figure shows the state of the container 6 within which the insulated coil la is arranged. The process is explained starting from preceeding processes without illustration in figures. First of all, a coil is made by winding a conductor and formed and then a tape such as grass backed mica tape which has been impregnated with an epoxy type semi-cured thermosetting resin is wound around the coil to form an insulated coil la.
~ 32~L73~
1 Next, the insulated coil la is placed into the container 6, wherein the insulated coil is embedded deeply into the solid particle bodies 5 to ensure that the insulated coil will not be exposed from the solid particle bodies.
In this case, the extensible member 11 serves as a closure of the container and thus the extensible member 11 must be attached by providing a sufficient sealing to ensure isolation of the inside of the container from the outside after the insulated coil has been inserted into the container.
Then the insulated coil is placed in the heating oven 16 together with a container by a truck.
If the insulated coil la is so small in siz.e that an operator can easily carry it by hand, the container 6 may be previously arranged within the heating oven 16 within which the insulated coil la is accommodated in the container.
Next, if a vacuum pump 15 is operated to reduce a reduced pressure within the container 6, the extensible member 11 is deformed as shown in Fig. 2, that is, atmospheric pressure P is applied to the external side of the extensive member and the solid particles receives the pressing force by the extensive member, so that whole surface of the layer of the insulating tape on the insulated coil is uniformly pressed in the same way as in the aforementioned example to improve the unlformity of the thickness and adhesion.
', .
~32~736 1 Then, under this condition, the insulated coil is heated and cured in the oven.
Particularly in case that the process for forming a film conducted in this way is employed, not only the same effect as the above-mentioned one is generated since the process is also the pressing and heating of the insulating film by solid particle bodies as mentioned in the above example, but also air remaining within the insulated coil is enforcedly drawn out of the film simultaneously with the pressing of the solid particles as the pressing means employs the deformation of a container by vacuum within the container, that is, voids are reduced and thus adhesion may be further improved than in the above-mentioned example.
Fig. 6 shows a further example.
Pressing force is obtained by reducing pressure (making a vacuum) within the container also in this case, and explanation will be conducted only referring to the different points from the above. There is a tightly closed container 6, which is divided into two rooms Rl and R2 up and down by the extensible member.
In the lower room R2, the solid particle bodies 5 and the insulated coil la are received, and reduced pressure is produced b~ a vacuum pump 15. On the other hand, the upper room Rl is connected with a vacuum pump or pressurizing pump 15a. Cooperation of the pressurizing pump 15a and the vacuum pump 15 in the lower room makes possible to press further stronger the solid particle ~32173~
1 bodies 5. Particularly if it is intended to make the inside of lower room Rl extremely lower vacuum condition and at the same time to retain the pressing force in a relatively low level, pressure in the lower room is reduced vigorously and a vacuum pump is connected also to the upper room to reduce a pressure so as to obtain the pressing force from the difference of the two reduced pressures. Thus it will be possible to control freely the degree of vacuum and the pressing force.
The present invention having been explained with reference to the several examples above, there ma~v also be used as the pressing means the expanding force of a heat expanding body by the use of the heat on heating a resin, the weight of the solid particle bodies or the combination thereof. There may be also considered a variety o~ methods such as compulsively pushing a number of the solid particle bodies into a tightly closed container having a predetermined volume or the like.
As the solid particles, those having a particle diameter of 10 - 800 ~ are optimal, and sand such as molding sand is most inexpensive and practical. It will be possible to employ any other particles such as metal balls, glass beads or the like which form space between the adjacent ones and retain air permeability on gathering together.
Having explained for the case of parts wherein one or more insulated films are formed on the surface ~ 32~73~
1 of a solid body and the one or more insulated films and the solid body are integrally used, the present invention is also applicable to the case of producing an insulating plate or insulating molded article by the use of a molding tool. That ls to say, when the insulating plate having a wave shape is intended to be produced, an insulating film having been impregnated with a resin is placed on the solid body having a wave-shaped surface and pressed in the solid particle bodies in the same manner as the aforementioned examples.
In this case, as the solid body and the insulating film are finally to be separated, it is needless ~o say that a release agent is preliminarily provided between the solid body and the insulating film. Insulating molded articles produced according to the process have no void in their layers and thus form a dense layer as those mentioned above, and it is also possible to obtain a layer having a uniform thickness along the shape of the surface of a solid body.
Next, one or more insulated films produced by the process of the present invention and the one produced by the conventional process are compared from the viewpoint of their effects.
Furthermore, it is difficult to evaluate the insulated coils produced by these processes from the viewpoint of their mechanical effects, that is, the degree of peeling and the results cannot be expressed specifically herein. However, it is well-known in the 11 3217~
l art that fewer voids in the insulating layer and uniform thickness of the insulating film over the whole surface will exhibit excellent properties in the insulated coil.
Fig. 7 is a test results of the insulated coil formed by the process of the present invention from the viewpoint of electri.c property which will be largely effected by the presence of void and shows the relationship between test voltage and tan ~ (%).
The insulated coil tested is a commutating-pole coil used for a direct current traction motor for a car (see Fig. 8), which has an oval shape with a total length of 320 mm and a total width of 100 mm, a rectangular section of 60 x 32 mm and a rated voltage of 400 V.
lS In Fig. 7, the curve X represented by a dotted line shows the test result of an insulated coil produced by the conventional process for forming a film, briefly saying, the one formed by pressing through a plate on the external side of the one or more films, wherein as i9 apparent from the figure tan ~ sharply increases at the test voltage higher than 2.5 kV.
The curve represented by a chain line y shows the result o~ an insulated coil produced by curing by applying oil pressure in an insulated oil, wherein tan ~, fluctuating little to the test voltage, is wholly in a higher level. On the other hand, the curve Z represented by a solid line shows a result of an insulated coil produced by the process of the present invention, wherein .
7 3 ~
1 as is apparent from the figure tan ~ remains wholly in a low level and will not increase largely.
Table 1 shows the results of measurement for evaluatin~ the uniformity of the insulation thickness of coils (see Fig. 8 with reference to the measuring point), wherein the thickness at the corner part t3 ~mean value) and those at the plain side parts t and t2 (mean value~ of the section of the insulated coil are particularly compared.
As is apparent from the result, there is no significant difference between the thicknesses at the plain parts in the coils formed by the conventional process and by the process of the present invention.
However, at the corner parts there is observed a remarkable improvement for the coil formed by the process of the present invention as compared with the one formed by pressing through a plate, and the coil produced by the process of the present invention has the same uniform thickness as in the coil produced by pressing in oil.
:~32~736 Table 1 _ Film formed by the .conventional processFilm formed by Measurlng the present pointthrough Pressing invention Interior1.5 mm 1.5 mm 1.5 mm gide (t2) L 1~4 1.5 l.S
part (t3) ~ 1.4 1.4 1 Table 2 shows the test result of dielectric breakdown voltages, which was carried out for four coils each.
Measurement were conducted by putting an aluminium foil as on electrode on the hollow part of Fig. 8, that is, the interior wall, and applying a voltage between the above electrode and a lead lb.
From the result, it will be apparent that the film formed by the process of the present invention can be resistant to a high voltage of about 10% higher than that applied to the one or more conventional films.
- 17 - :
~321~36 Table 2 Film formed by the conventional process _ Fllm formed by a plate Pressing the present ~... _ ._ .
18.0 19.0 21.5 Breakdown 18.0 20.0 22.0 voltage (kV) 19.0 20.0 22.0 19.0 21.0 23.0 Mean value 18.5 20.0 22.1 1 [EFFECTS OF THE INVENTION]
As mentioned above in detail, according to the present invention when an impregnated resin in an insulating film is cured while pressing the film a large number of solid particle bodies are densely provided on the external surface of the insulating film, the insulating film is pressed onto the surface of the solid body through the solid particle bodies and the impregnated resin is cured in that state. Therefore, the insulating film is uniformly pressed through the surrounding solid particle bodies irrespect1ve of the corner part, deformed part or curved part of the sol1d body, and air between the insulating film and the solid :
body and within the insulating film layer is expelled - 18 ~
~32:~36 1 out of the layer through the space between the solid particle bodies, so that one or more insulated films having a uniform thickness as a whole and no remaining air and excellent in adhesion can be obtained.
- 19 -:
Claims (10)
1. A process for forming one or more insulated films on the surface of a solid body comprising pressing towards said solid body one or more insulated films which are so arranged as to cover at least a part of said solid body and are impregnated with a resin and at the same time curing said impregnated resin, characterized in that on curing said impregnated resin while pressing said one or more insulated films a large number of solid particle bodies are densely provided on the external surface of said one or more insulated films, said one or more insulated films are pressed onto the surface of the solid body through said solid particle bodies and the impregnated resin is cured in that state.
2. A process for forming one or more insulated films on the surface of a solid body according to Claim 1, wherein the particle diameter of said solid particle bodies is in the range of 10 µ - 800 µ.
3. A process for forming one or more insulated films on the surface of a solid body comprising pressing from the exterior side of the one or more insulated films to said solid body with a predetermined pressure one or more insulated films which are so arranged as to cover at least a part of said solid body and are impregnated with a resin and at the same time curing said impregnated resin, characterized in that on curing said impregnated resin while pressing said one or more insulated films said solid body covered with said one or more insulated films is embedded into solid particle bodies and at the same time pressing force is applied to the solid particle bodies, so that said impregnated resin is cured in that state.
4. A process for forming one or more insulated films on the surface of a solid body comprising pressing towards said solid body one or more insulated films which are so arranged as to cover at least a part of said solid body and are impregnated with a resin and at the same time curing said impregnated resin, characterized in that on curing said impregnated resin while pressing said one or more insulated films said solid body covered with said one or more insulated films is placed together with solid particle bodies in a tightly closed container having a variable volume and then said volume of said tightly closed container is reduced to a level wherein a predetermined pressing force is generated between said solid particles, so that said impregnated resin is cured in that state.
5. A process for forming one or more insulated films on the surface of a solid body comprising pressing towards said solid body one or more insulating films which are so arranged as to cover at least a part of said solid body and are impregnated with a resin and at the same time curing said impregnated resin, characterized in that on curing said impregnated resin while pressing said one or more insulated films said solid body covered with said one or more insulated films is placed together with solid particle bodies in a tightly closed container having a predetermined volume and then said solid particle bodies are compulsively charged into said tightly closed container and a predetermined pressing force is applied between the solid particle bodies, so that said impregnated resin is cured in that state.
6. A process for forming one or more insulated films on the surface of a solid body comprising pressing to said solid body with a predetermined pressure one or more insulated films which are so arranged on the surface of the solid body as to cover at least a part of said solid body and are impregnated with a resin and at the same time curing said impregnated resin, characterized in that on curing said impregnated resin while pressing said one or more insulated films said solid body covered with said one or more insulated films is placed in a tightly closed container in which solid particle bodies are placed so that said solid body is embedded into solid particle bodies, then the inside pressure of the said tightly closed container is reduced and at the same time pressing force is applied to ensure that the volume of the solid particle bodies including the solid body will be reduced and said impregnated resin is cured in that state.
7. A process for forming one or more insulated firms on the surface of a solid body comprising pressing towards said solid body one or more insulated films which are so arranged as to coyer at least a part of said solid body and are impregnated with a thermosetting resin and at the same time curing said impregnated resin, characterized in that on curing said impregnated resin while pressing said one or more insulated films, said solid body covered with the said one or more insulated films is embedded into solid particle bodies placed in a tightly closed container at least a part of which is deformable, then the inside pressure of said tightly closed container is reduced so as to deform a part of the tightly closed container and the deforming force of the container is applied to said one or more insulated films through said solid particle bodies, so that said impregnated resin is cured in that state.
8. A process for forming one or more insulated films pressing to a solid body having a predetermined shape one or more insulated films which are arranged on the surface of said solid body and are impregnated with a resin, at the same time curing said impregnated resin, forming the one or more insulated films in the shape of the surface of the solid body by using the surface of the solid body as a guide and separating the one or more insulated films from the solid body after curing the impregnated resin, characterized in that on curing said impregnated resin while pressing said one or more insulated films said one or more insulated films are placed on said solid body and embedded into solid particle bodies together with said solid body, and pressing force is externally applied to said solid particle bodies, so that said impregnated resin is cured in that state.
9. An apparatus for forming one or more insulated films on the surface of a solid body comprising pressing to the solid body one or more insulated films which are so arranged as to cover at least a part of the solid body and are impregnated with a resin and at the same time heat-curing said impregnated resin, characterized in that a container for receiving said solid body which is covered with said one or more insulated films, said particle bodies which are put in said container and in which said solid body has been embedded and a pressing means for applying pressing force to said solid particle bodies are provided, so that the pressing force by said pressing means is applied to said one or more insulated films through said solid particle bodies.
10. An apparatus for forming one or more insulated films on the surface of a solid body by pressing to the solid body and one or more insulated films which are so arranged as to cover at least a part of the solid body and are impregnated with a resin and at the same time heat curing said impregnated resin, characterized in that a tightly closed container in which said solid body covered with said one or more insulated films is placed and a volume of which is varied by the difference of the pressures between the interior and exterior thereof, solid particle bodies which are almost fully put in said tightly closed container and in which said solid body is embedded and a means for reducing the inside pressure of said tightly closed container and reducing the volume of the container are provided, so that the force generated by reducing the volume of said container is applied to said one or more insulated films through said solid particle bodies.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62-50058 | 1987-03-06 | ||
| JP62050058A JPS63217611A (en) | 1987-03-06 | 1987-03-06 | Method and device for forming insulating film on solid object surface |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1321736C true CA1321736C (en) | 1993-08-31 |
Family
ID=12848398
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000558880A Expired - Fee Related CA1321736C (en) | 1987-03-06 | 1988-02-15 | Process for forming one or more insulated films on the surface of a solid body and an apparatus therefor |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS63217611A (en) |
| KR (1) | KR960001144B1 (en) |
| AU (1) | AU605238B2 (en) |
| CA (1) | CA1321736C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113400649A (en) * | 2021-06-30 | 2021-09-17 | 山东威高骨科材料股份有限公司 | Method for solving thermal deformation of PEEK (polyetheretherketone) material part during 3D printing |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2886948B2 (en) * | 1990-05-30 | 1999-04-26 | 株式会社日立製作所 | Method of forming insulating film on surface of solid object |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS51650A (en) * | 1974-06-21 | 1976-01-06 | Hitachi Ltd | DENKIZET SUENSENRINNO SEIZOHOHO |
| JPS5193323A (en) * | 1975-02-14 | 1976-08-16 | Denkikikisenrinno seizosochi |
-
1987
- 1987-03-06 JP JP62050058A patent/JPS63217611A/en active Granted
-
1988
- 1988-02-04 AU AU11294/88A patent/AU605238B2/en not_active Ceased
- 1988-02-10 KR KR1019880001265A patent/KR960001144B1/en not_active IP Right Cessation
- 1988-02-15 CA CA000558880A patent/CA1321736C/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113400649A (en) * | 2021-06-30 | 2021-09-17 | 山东威高骨科材料股份有限公司 | Method for solving thermal deformation of PEEK (polyetheretherketone) material part during 3D printing |
| CN113400649B (en) * | 2021-06-30 | 2023-07-04 | 山东威高骨科材料股份有限公司 | Method for solving thermal deformation of 3D printing PEEK material part |
Also Published As
| Publication number | Publication date |
|---|---|
| KR880011833A (en) | 1988-10-31 |
| JPS63217611A (en) | 1988-09-09 |
| JPH0478163B2 (en) | 1992-12-10 |
| KR960001144B1 (en) | 1996-01-19 |
| AU1129488A (en) | 1988-09-08 |
| AU605238B2 (en) | 1991-01-10 |
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