GB2037087A - A transformer covered with thermoplastic resin and a method for covering it - Google Patents
A transformer covered with thermoplastic resin and a method for covering it Download PDFInfo
- Publication number
- GB2037087A GB2037087A GB7847931A GB7847931A GB2037087A GB 2037087 A GB2037087 A GB 2037087A GB 7847931 A GB7847931 A GB 7847931A GB 7847931 A GB7847931 A GB 7847931A GB 2037087 A GB2037087 A GB 2037087A
- Authority
- GB
- United Kingdom
- Prior art keywords
- bobbin
- resin
- coat
- transformer
- mold
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
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
- H01F41/005—Impregnating or encapsulating
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F27/00—Details of transformers or inductances, in general
- H01F27/02—Casings
- H01F27/022—Encapsulation
Abstract
A transformer is disclosed which comprises a core 2, a bobbin 3, and coils 4 wound around the bobbin, wherein the bobbin is made of a thermoplastic resin, and a surrounding coat 5 is made of a thermoplastic resin which either is the same material as that of the bobbin, or has similar thermal expansion coefficient thereto, and a good chemical affinity therefor. Further, a method is disclosed (Fig. 3 not shown) for performing such covering, which may include supporting the assembly comprising the core, the bobbin, and the coils by the bobbin upon a bobbin support (18) made of the same material as the coat inside a mold, and introducing the material of the coat into the mold. Specified resins include polyamide, polyester polyethylene, polypropylene, polystyrene, polyaoetal, polymethyl methacrylate, ABS, polystyrene-co-acrylonitrile and polyurethane resins. <IMAGE>
Description
SPECIFICATION
A transformer covered with thermoplastic resin, and a method for covering it
This invention relates to a transformer covered with a coat of thermoplastic resin, and to a method for covering a transformer with a coat of thermoplastic resin by molding.
A conventional transformer is often covered, by molding, with a coat of thermosetting resin, such as phenol resin, urea resin, melamine resin, Xylene resin, unsaturated polyester resin, or epoxy resin. This is done by placing in the center of a mold the transformer, which comprises a core, a bobbin attached thereto, and coils wound around the bobbin, and by filling or injecting thermosetting resin into the mold. The resin is then cured.
However, when this is done, reaction gases generated in the resin often remain in the form of trapped bubbles of gas attached to the surfaces of the bobbin, the coils, and the core, and this lowers the quality of the resultant product. Since the adhesion of the thermosetting resin to the transformer is bad, it is impossible to remove these bubbles completely.
Because of these bubbles, heat transmission to the resin material is uneven, and therefore local hot spots are caused, which often results in cracks in the thermosetting resin.
The bobbin of the transformer is generally made of a thermoplastic resin. Because the adhesion properties between this thermoplastic resin and the thermosetting resin of the coating is bad, and because these resins usually have very different thermal expansion characteristics, again cracks may be caused in use.
Furthermore, when the transformer is covered by a system of molding such as casting molding, compression molding, transfer molding, injection molding, or the like, it is very difficult to keep the transformer positioned accurately in the center of the mold, without distorting the bobbin, the coils, of the core.
And if the molding is performed while the transformer is off-center in the mold, part of the resin coating will be too thin, which will result in low insulating capacity.
If, in order to hold the transformer accurately in the center of the mold, it is supported by parts of the mold itself, when the molding is completed parts of the transformer are not covered, but holes are left in the coating of resin. Even if these are crudely stopped up later, insulating capacity is lowered, and water-resistance is also lower than is desirable.
Therefore, it is an object of the present invention to provide a transformer covered with thermoplatic resin free from the abovementioned defects and having good electrical properties, such as high insulating capacity, good resistance to water and other chemicals, and so forth.
It is another object of the present invention to provide a method for covering a transformer with a coat of thermoplastic resin by molding, free from the above-mentioned defects, which produces a transformer with the desirable properties outlined above.
According to the present invention, there is provided a transformer comprising a core, a bobbin made of thermoplastic resin fitted over part of the core, and coils fitted over the bobbin, characterized in that it is covered substantially entirely by a coat of thermoplastic resin which has approximately the same thermal expansion coefficient as the material of the bobbin, and has a good chemical affinity therefor.
Further, according to the present invention there is provided a method of covering a transformer, comprising covering a core, a bobbin made of thermoplastic resin fitted over part of the core, and coils fitted over the bobbin, with a coat of thermoplastic resin which has approximately the same thermal expansion coefficient as the material of the bobbin, and which has a good chemical affinity for the bobbin, by molding.
As a preferred possibility, the material of the bobbin and of the coat may be the same.
of polyamide resin, polyester resin, polyethylene resin, polypropylene resin, polystyrene resin, polyacetal resin, polymethyl methacrylate resin, ABS resin, polystyrene-co-acrylonitrile resin, polyurethane resin, and the like.
In order that the present invention may be better understood, preferred embodiments will now be described with reference to the accompanying drawings, which are given for purposes of illustration only, and thus are not limitative of the present invention, and wherein:
Figure 1 is a vertical cross-section of a transformer molded according to the present invention;
Figure 2 is a horizontal cross-section, taken along the line ll-ll in Fig. 1;
Figure 3 is a longitudinal sectional front view of another transformer set up in a mold to be molded according to the present invention;
Figure 4 is a longitudinal sectional side view taken along the line IV-IV in Fig. 3;
Figure 5 is a perspective view of a bobbin support used in the molding process for which the set-up is shown in Fig. 3;
Figure 6 is a perspective view of the bobbin of the transformer shown in Fig. 3;;
Figure 7 is a longitudinal sectional front view of still another transformer set up in a mold to be molded according to the present invention;
Figure 8 is a longitudinal sectional side view, taken along the line VIII-VIII in Fig. 7; and Figure 9 is a perspective view of a peg which may be used as an alternative to the projections shown as projecting from the bobbin of the transformer of Figs. 7 and 8.
In Figs. 1 and 2 there is shown a transformer 1 which comprises a core 2 having a central cross portion 2a, a bobbin 3 fitted on the central cross portion 2a, and coils 4 fitted on the bobbin 3, and which is covered substantially entirely with a molded coat 5 of thermoplastic resin in a mold 6, by such molding as casting, compression molding, injection molding, transfer molding, or the like.
The core 2 may be composed of a combination of E-shaped and I-shaped plates of wellknown design. The bobbin 3 is made of a thermoplastic resin which has approximately the same thermal expansion coefficient as does the material of the molded coat 5, and which has a good chemical affinity, i.e. wetting action, for the material of the coat 5, and therefore even when the temperature of the transformer rises during use no thermal stress occures between the coat and the bobbin, and therefore no cracks will occur. Further, because of the good chemical affinity between the materials of the coat and the bobbin, they adhere tightly together after molding, and thereby good airtightness and good heat transmission characteristics of the transformer are provided.
As a possible modification, the material of the bobbin and the material of the molded coat may be quite identical. Thus the best possible matching of the physical properties of the two parts is of course attained. However since the bobbin is formed, for instance, by ordinary molding, and the coat is formed, for instance, by injection molding, it may not be suitable to use exactly the same plastic material for both of them, and therefore the possibility is to be considered that two somewhat different resins should be used, which match up sufficiently well in the relevant characteristics-i.e., thermal expansion coefficient and chemical affinity, i.e. wetting characteristics. The similarity in these two properties will assure desirable freedom of the transformer from cracking in use, and from bubble formation during manufacture.
According to the present invention, after the transformer 1 has been placed in the center of the mold 6, thermoplastic resin 5 is injected into the mold, and thereby the transformer 1 is covered with a good coat. Then the mold 6 is cooled.
In Figs. 3 and 4 is shown another transformer set up in a mold ready for coating, which is to be coated according to the present invention.
The transformer 11 which comprises a core 1 2 having a central cross portion 1 2a, a bobbin 1 3 fitted on the central cross portion 1 2a, and coils 1 4 fitted on the bobbin, is positioned in the center of the hollow 1 7 of a mold 1 6 which is made of an upper mold 1 6a and a lower mold 16b, on a bobbin supprt 1 8 placed on the upper surface of the lower mold 16b.
In Fig. 5 is shown the bobbin support 18 for supporting the bobbin 1 3. This bobbin support is made of thermoplastic resin, which again has approximately the same thermal expansion coefficient as the material of the molded coat, and has a good chemical affinity therefor, for the same reasons as above.
Again, the bobbin support may be made of exactly the same material as the coat, or on the other hand it may be of a material which is similar in the relevant characteristics, and which is easily bonded thereto. The bobbin support comprises a center flat part 1 9 and a pair of side parts 20 which project a little downwards and have longitudinal grooves 21 formed in them. A plurality of vertical holes 22 are arranged along the longitudinal grooves 21.
In Fig. 6 is shown the bobbin 13, which is made, according to the present invention, as previously explained, out of a thermoplastic material which has approximately the same thermal expansion coefficient as the material of the coat, and which has a good chemical affinity for the material of the coat. This bobbin 1 3 comprises a body 22 on which the coils 4 are fitted, and a pair of end plates 23, a center partition plate 24, and a pair of bobbin legs 25 which are integrally coupled to the lower ends of the end plates 23.
Terminal pins 26 for connecting the coil leads are fixed to the bobbin legs 25 and project downwards therefrom.
As clearly shown in Figs. 3 and 4, a groove 27 is formed in the upper surface of the lower mold 16b. The shape of this groove 27 is arranged to conform exactly to the lower surface of the bobbin support 18, and it includes terminal pin holes 28 projecting downwards in the lower mold 16b, into which the terminal pins 26 are inserted through the vertical holes 22 of the bobbin support 1 8.
The bobbin support 1 8 is fitted onto the groove 27 of the lower mold 16b, and the bobbin legs 25 of the bobbin 1 3 are fitted onto the longitudinal grooves 21 of the bobbin support 18, as shown in Figs. 3 and 4, and thereby the transformer 11 is exactly and strongly held at a suitable place in the mold.
Consequently, when the molding is performed by injecting the thermoplastic resin into the hollow 1 7 of the mold 16, the transformer 11 does not move from the predetermined position in the mold 16, and thereby is obtained a transformer covered with a coat of thermoplastic resin (part of which is constituted by the bobbin support 1 8) which has a uniform thickness. The only parts of the transformer which project are the terminal pins 26.
In Figs. 7 and 8 a different embodiment of
the present invention is shown. The bobbin
end plates 23 are provided with projections
23a on their upper sides which bear against the bottom of the upper mold 16a, and
thereby the transformer is more strongly fixed
in the mold than in the arrangement of Figs.
3 and 4.
As another possibility, instead of providing
these projections 23a projecting upwards
from the bobbin end plates, separate pegs
such as shown by 29 in Fig. 9 may be
provided. These are fitted in between the
bobbin end plates and the mold on the upper
side, i.e. the side remote from the bobbin support 18, and fulfil the same functions as the projections 23a in the device of Figs. 7
and 8.
The material from which these pegs are
made, again, should be a thermoplastic
material which has approximately the same thermal expansion coefficient as the material of the coat, and has a good chemical affinity therefor. As a preferred embodiment, it may
be the same material.
Although the invention has been shown and described with respect to some preferred embodiments thereof, it should be understood by those skilled in the art that various changes and omissions in the form and the content thereof may be made without departing from the scope of the invention. Therefore, it is desired that the scope of the protection granted should not be limited by any details of the embodiments shown, or of the drawings, which were given for illustration only, but only by the appended claims.
Claims (21)
1. A transformer comprising a core, a bobbin made of thermoplastic resin fitted over part of the core, and coils fitted over the bobbin,
characterized in that it is covered substantially entirely by a coat of thermoplastic resin which has approximately the same thermal expansion coefficient as the material of the bobbin, and has a good chemical affinity therefor.
2. A transformer according to claim 1, wherein the material of the coat is the same as the material of the bobbin.
3. A transformer according to claim 1 or claim 2, wherein the thermoplastic materials of the coat and the core are selected from the group consisting of polyamide resin, polyester resin, polyethylene resin, polypropylene resin, polystyrene resin, polyacetal resin, polymethyl methacrylate resin, ABS resin, polystyrene-coacrylonitrile resin, and polyurethane resin.
4. A method of covering a transformer which comprises covering a core, a bobbin made of thermoplastic resin fitted over part of the core, and coils fitted over the bobbin, with a coat of thermoplastic resin which has approximately the same thermal expansion coefficient as the material of the bobbin, and which has a good chemical affinity for the
bobbin, by molding.
5. A method according to claim 4, wherein the material of the coat is the same as the material of the bobbin.
6. A method according to claim 4, wherein the material of the coat and the
material of the bobbin are each selected from the group consisting of polyamide resin, polyester resin, polyethylene resin, polypropylene resin, polystyrene resin, polyacetal resin, polymethyl methylacrylate resin, ABS resin, polystyrene-co-acrylonitrile resin, and polyurethane resin.
7. A method according to claim 5, wherein the material of the coat and the bobbin is selected from the group consisting of polyamide resin, polyester resin, polyethylene resin, polypropylene resin, polystyrene resin, polyacetal resin, polymethyl methylacrylate resin, ABS resin, polystyrene-co-acrylonitrile resin, and polyurethane resin.
8. A method according to any of claims 4 through 7, wherein the molding takes place in a mold, and before the thermoplastic material of the coat is injected into the mold the assembly comprising the core, the bobbin, and the coils is supported in the mold by the bobbin on a bobbin support which is composed of a thermoplastic material which has approximately the same thermal expansion coefficient as the material of the coat, and which has a good chemical affinity therefor.
9. A method according to claim 8, wherein the material of the bobbin support is the same as the material of the coat.
10. A method according to claim 8, wherein terminal pins are incorporated into the transformer, and these project through the bobbin support and are received in holes in the mold during the molding process.
11. A method according to claim 10, wherein the material of the bobbin support is the same as the material of the coat.
1 2. A method according to claim 8, wherein the bobbin is provided with projections which bear against the inside of the mold remote from the bobbin support.
1 3. A method according to claim 10, wherein the bobbin is provided with projections which bear against the inside of the mold remote from the bobbin support.
1 4. A method according to claim 9, wherein the bobbin is provided with projections which bear against the inside of the mold remote from the bobbin support.
1 5. A method according to claim 11, wherein the bobbin is provided with projections which bear against the inside of the mold remote from the bobbin support.
16. A method according to claim 8, wherein pegs are provided which extend from the bobbin to the inside of the mold remote from the bobbin support, said pegs being made of a thermoplastic material which has approximately the same thermal expansion coefficient as the material of the coat, and which has a good chemical affinity therefor.
17. A method according to claim 16, wherein the material of the pegs is the same as the material of the coat.
18. A method according to claim 16, wherein the material of the bobbin support is the same as the material of the coat.
1 9. A method according to claim 17, wherein the material of the bobbin support is the same as the material of the coat.
20. A transformer, substantially as hereinbefore described, with reference to any of
Figs. 1 and 2, 3 to 6, 7 and 8, or 9 of the accompanying drawings.
21. A method of covering a transformer, substantially as hereinbefore described, with reference to any one of Figs. 1 and 2, 3 to 6, 7 and 8, or 9 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7847931A GB2037087A (en) | 1978-12-11 | 1978-12-11 | A transformer covered with thermoplastic resin and a method for covering it |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7847931A GB2037087A (en) | 1978-12-11 | 1978-12-11 | A transformer covered with thermoplastic resin and a method for covering it |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2037087A true GB2037087A (en) | 1980-07-02 |
Family
ID=10501640
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7847931A Withdrawn GB2037087A (en) | 1978-12-11 | 1978-12-11 | A transformer covered with thermoplastic resin and a method for covering it |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2037087A (en) |
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4460535A (en) * | 1980-12-22 | 1984-07-17 | Hitachi, Ltd. | Method for producing flyback transformers |
| GB2161028A (en) * | 1982-07-20 | 1986-01-02 | British Broadcasting Corp | Audio transformers for safety isolation |
| GB2222983A (en) * | 1988-07-12 | 1990-03-28 | Honda Motor Co Ltd | Molding of foam resin having a hollow preformed member. |
| EP0544477A1 (en) * | 1991-11-26 | 1993-06-02 | Matsushita Electric Industrial Co., Ltd. | Molded transformer |
| GB2284102A (en) * | 1993-11-18 | 1995-05-24 | Anthony James Doyle | Inductors |
| EP0671778A2 (en) * | 1994-03-09 | 1995-09-13 | Standex International Corporation | Antenna coil assembly for an automobile transponder key system |
| US6198373B1 (en) * | 1997-08-19 | 2001-03-06 | Taiyo Yuden Co., Ltd. | Wire wound electronic component |
| EP1508384A2 (en) * | 2003-08-19 | 2005-02-23 | Minebea Co., Ltd. | System and method for applying varnish to an electrical coil |
| WO2011092097A1 (en) | 2010-01-29 | 2011-08-04 | Abb Research Ltd | An electric device and a method for manufacturing the device |
| GB2483344A (en) * | 2010-09-03 | 2012-03-07 | Rs Isolsec S L | Resin embedded transformer and its method of manufacture |
| WO2013027167A3 (en) * | 2011-08-23 | 2013-05-30 | Sabic Innovative Plastics Ip B.V. | A molded article having enhanced aesthetic effect and method and system for making the molded article |
| US8502635B2 (en) * | 2004-07-17 | 2013-08-06 | Carl Freudenberg Kg | Magnetostrictive element and use thereof |
| US20150316395A1 (en) * | 2012-12-20 | 2015-11-05 | Continental Teves Ag & Co. Ohg | Sensor for detecting the position of an encoder element |
| CN114054314A (en) * | 2021-12-20 | 2022-02-18 | 宁波金坦磁业有限公司 | Method for coating high-stability coating on surface of neodymium iron boron substrate |
| CN114210519A (en) * | 2021-12-20 | 2022-03-22 | 宁波金坦磁业有限公司 | Automatic change coating equipment |
-
1978
- 1978-12-11 GB GB7847931A patent/GB2037087A/en not_active Withdrawn
Cited By (26)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4460535A (en) * | 1980-12-22 | 1984-07-17 | Hitachi, Ltd. | Method for producing flyback transformers |
| GB2161028A (en) * | 1982-07-20 | 1986-01-02 | British Broadcasting Corp | Audio transformers for safety isolation |
| GB2222983A (en) * | 1988-07-12 | 1990-03-28 | Honda Motor Co Ltd | Molding of foam resin having a hollow preformed member. |
| GB2222983B (en) * | 1988-07-12 | 1992-07-01 | Honda Motor Co Ltd | Molding of foam resin having a hollow member |
| EP0544477A1 (en) * | 1991-11-26 | 1993-06-02 | Matsushita Electric Industrial Co., Ltd. | Molded transformer |
| US5977855A (en) * | 1991-11-26 | 1999-11-02 | Matsushita Electric Industrial Co., Ltd. | Molded transformer |
| GB2284102A (en) * | 1993-11-18 | 1995-05-24 | Anthony James Doyle | Inductors |
| EP0671778A2 (en) * | 1994-03-09 | 1995-09-13 | Standex International Corporation | Antenna coil assembly for an automobile transponder key system |
| EP0671778A3 (en) * | 1994-03-09 | 1996-06-26 | Standex Int Corp | Antenna coil assembly for an automobile transponder key system. |
| SG102695A1 (en) * | 1997-08-19 | 2005-05-30 | Taiyo Yuden Kk | Wire wound electronic component |
| US6198373B1 (en) * | 1997-08-19 | 2001-03-06 | Taiyo Yuden Co., Ltd. | Wire wound electronic component |
| EP1508384A3 (en) * | 2003-08-19 | 2005-04-06 | Minebea Co., Ltd. | System and method for applying varnish to an electrical coil |
| EP1508384A2 (en) * | 2003-08-19 | 2005-02-23 | Minebea Co., Ltd. | System and method for applying varnish to an electrical coil |
| US8502635B2 (en) * | 2004-07-17 | 2013-08-06 | Carl Freudenberg Kg | Magnetostrictive element and use thereof |
| WO2011092097A1 (en) | 2010-01-29 | 2011-08-04 | Abb Research Ltd | An electric device and a method for manufacturing the device |
| GB2483344B (en) * | 2010-09-03 | 2014-12-17 | Rs Isolsec S L | Resin embedded transformer and manufacturing procedure therefore |
| GB2483344A (en) * | 2010-09-03 | 2012-03-07 | Rs Isolsec S L | Resin embedded transformer and its method of manufacture |
| WO2013027167A3 (en) * | 2011-08-23 | 2013-05-30 | Sabic Innovative Plastics Ip B.V. | A molded article having enhanced aesthetic effect and method and system for making the molded article |
| US8557158B2 (en) | 2011-08-23 | 2013-10-15 | Sabic Innovative Plastics Ip B.V. | Molded article having enhanced aesthetic effect and method and system for making the molded article |
| US9975312B2 (en) | 2011-08-23 | 2018-05-22 | Sabic Global Technologies B.V. | Molded article having enhanced aesthetic effect and method and system for making the molded article |
| US20150316395A1 (en) * | 2012-12-20 | 2015-11-05 | Continental Teves Ag & Co. Ohg | Sensor for detecting the position of an encoder element |
| US10690516B2 (en) * | 2012-12-20 | 2020-06-23 | Continental Teves Ag & Co. Ohg | Protective compound-enveloped sensor for detecting the position of an encoder element |
| CN114054314A (en) * | 2021-12-20 | 2022-02-18 | 宁波金坦磁业有限公司 | Method for coating high-stability coating on surface of neodymium iron boron substrate |
| CN114210519A (en) * | 2021-12-20 | 2022-03-22 | 宁波金坦磁业有限公司 | Automatic change coating equipment |
| CN114210519B (en) * | 2021-12-20 | 2022-10-18 | 宁波金坦磁业有限公司 | Automatic change coating equipment |
| CN114054314B (en) * | 2021-12-20 | 2023-02-24 | 宁波金坦磁业有限公司 | Method for coating high-stability coating on surface of neodymium iron boron substrate |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |