WO2006071182A1 - Improved manufacture of toroidal transformers - Google Patents
Improved manufacture of toroidal transformers Download PDFInfo
- Publication number
- WO2006071182A1 WO2006071182A1 PCT/SE2005/002024 SE2005002024W WO2006071182A1 WO 2006071182 A1 WO2006071182 A1 WO 2006071182A1 SE 2005002024 W SE2005002024 W SE 2005002024W WO 2006071182 A1 WO2006071182 A1 WO 2006071182A1
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- WIPO (PCT)
- Prior art keywords
- ribbon
- bobbin
- inner cavity
- combined component
- opening
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Classifications
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- 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
- H01F41/0206—Manufacturing of magnetic cores by mechanical means
- H01F41/0213—Manufacturing of magnetic circuits made from strip(s) or ribbon(s)
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- 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
- H01F41/06—Coil winding
- H01F41/08—Winding conductors onto closed formers or cores, e.g. threading conductors through toroidal cores
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- 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
- H01F41/06—Coil winding
- H01F41/098—Mandrels; Formers
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
- Coils Or Transformers For Communication (AREA)
- Insulating Of Coils (AREA)
Abstract
The present invention relates to a novel and efficient method for manufacture of toroidal transformers, a first bobbin and a second bobbin for manufacture of toroidal transformers and a system for performing said method for manufacture of toroidal transformers . Said method for manufacture of toroidal transformers has properties superior for automated mass production and comprises the steps of arranging a coil around the periphery of at least one first bobbin of elongated shape and of flexible material, providing at least one second bobbin, said second bobbin being essentially shaped as a circular segment and having at least one first inner cavity and at least one second inner cavity arranged around and along said at least one first inner cavity, feeding said at least one first bobbin, together with said coil, into said at least one second bobbin around said at least one first inner cavity, so that said coil is packed in said at least one second inner cavity, forming a component being essentially shaped as a circular segment, wherein at least one of said component ends defines an opening, joining at least two of said components together, so that a combined component is formed, wherein at least one of said combined component ends defines an opening, and feeding a ribbon of magnetic material through said opening, so that said ribbon is being wound a required amount of tightly packed winding turns inside said at least one first inner cavity until essentially the whole at least one inner cavity of said combined component is filled, said ribbon thereby forming a core .
Description
IMPROVED MANUFACTURE OF TOROIDAL TRANSFORMERS
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a novel and efficient method for manufacture of toroidal transformers, a first and a second support structure for manufacture of toroidal transformers and a system for performing said method for manufacture of toroidal transformers .
BACKGROUND ART
Many suggestions have been made to provide a toroidal transformer having a wound, circular shaped core and windings surrounding the core. The lion's share of prior art suggestions comprises a winding process in which the coil is wound on a continuous toroidal-shaped core using conventional winding machines. Most commonly the coil is repeatedly threaded through the empty center hole in the transformer. There is also method using a slave roller as shown, for example, in US patent 4,771,957.
Alternatively, some suggestions have been made on how to feed a continuous or nearly continuous core material into preformed windings. One early example of such an effort is shown in US patent 2,191,393. Other examples are provided in US patents 6,145,774, 4,765,861, and 4,896,839.
In US patent 4,779,812, the high voltage winding is wound into a number of wedge-shaped bundles, which then are arranged into two preformed, semi-circular transformer sections, each corresponding to about one- half of the transformer. Each wedge-shaped segment is wound and formed from a continuous wire, but only between 30 to 50 percent of the total length of voltage coil is allowed to be wound from a continuous wire. A single, continuous, ribbon-like strip, or a number of strips in parallel arrangement, is then fed through a gap between adjacent ends of the semi-circular sections and wound in place into an arcuate elongated passage formed in said sections to form a magnetic core. Belt means, engaging the radially-outward winding of said magnetic core as it is being wound within said arcuate elongated passage, is used to facilitate the winding of said core.
The device shown in US 4,779,812 is mainly intended for manufacture of very large toroids that are not applicable in ordinary electrical equipment, such as adaptors. Furthermore, the individual winding of the many wedge-shaped bundles and arranging them so that said arcuate elongated passage is formed, and the subsequent feeding of the ribbon into said passage is a cumbersome, relatively labour-intensive and time-consuming process, not suitable for automated mass production of transformers .
Evidently, there is a need for a method with which it is possible to effectively manufacture toroidal transformers at lower production costs, especially adapted for automated mass-production of transformers that are suitable for use in electrical equipment, such as adaptors .
GENERAL DISCLOSURE OF THE INVENTION
The key object of the present invention is to mitigate limitations related to the types described above.
An object of the present invention is to provide a method and a system for manufacture of toroidal transformers, having properties superior for automated mass production. Another object of the present invention is to provide toroidal transformers characterised by low production costs, lower no-load losses, higher efficiency, low weight and little volume, making them especially suitable for use in electrical equipment, such as adaptors.
According to a first aspect of the present invention, it relates to a method for manufacture of toroidal transformers, the method comprising the steps of arranging a coil around the periphery of at least one first bobbin of elongated shape and of flexible material; providing at least one second bobbin, said second bobbin being essentially shaped as a circular segment and having at least one first inner cavity and at least one second inner cavity arranged around and along said at least one first inner cavity, feeding said at least one first bobbin, together with said coil, into said at least one second bobbin around said at least one first inner cavity, so that said coil is packed in said at least one second inner cavity, forming a component being essentially shaped as a circular segment, wherein at least one of said component ends defines an opening, joining at least two of said components together, so that a combined component is formed, wherein at least one of
said combined component ends defines an opening, and feeding a ribbon of magnetic material through said opening, so that said ribbon is being wound a required amount of tightly packed winding turns inside said at least one first inner cavity until essentially the whole at least one inner cavity of said combined component is filled, said ribbon thereby forming a core.
When joining said at least two of said components together, so that a combined component is formed, in the case, for example, where two of said components are joined together, one of these components may carry a primary winding and the other component may carry a secondary winding.
The present invention solves problems in the prior art associated with winding the coil on a continuous toroidal core using conventional winding machines. Conventionally, there are two different winding processes in the prior art. Firstly, and most commonly, the coil is repeatedly threaded through the empty center hole in the transformer. Secondly, there is a method using a slave roller as shown, for example, in US patent 4,771,957. In the present invention this slave roller is replaced by a process in which the coil is first wound on a periphery of a straight bobbin. This approach significantly simplifies and speeds up the winding of the coil as compared to both methods known in the prior art.
Further, the process according to the present invention, in which the coil is wound on a periphery of a straight bobbin, allows for the whole coil to be wound in one single fast operation, while this is not the case for the solution presented in US patent 4,779,812, in which the wedge-shaped segments commonly only allow between 30 to 50 percent of the total length of voltage coil to be
wound from a continuous wire, which lowers the efficiency of the transformer.
Furthermore, the present invention makes it possible to decrease the relative size of the empty center hole of the transformer, since this hole, in principle, is not needed to enable the winding process when using the method according to the present invention. The reduced size of the center hole leads to a shorter magnetic path length (MPL) , which means that fewer coil windings need to be wound and that it is easier to reach a higher flow. This also makes it possible to reduce the relative size of the whole transformer, making it even more suitable to use in various electronic equipment.
According to a preferred embodiment of the method according to the present invention, it comprises the additional step of cutting said ribbon at a desired length after having fed said ribbon through said opening. The step of cutting the ribbon after having fed said ribbon through said opening brings about the particular advantage that one need not, necessarily, to pre-cut the ribbon before starting the feeding step, which means significant time savings as compared to the case where one needs to pre-cut the ribbon in matched lengths in advance. Rather, according to the present invention, it is possible to perform the feeding step using ribbon rolls directly as they come from the supplier. This means that the present method is cheaper, simpler and more suitable for mass production.
According to another preferred embodiment of the method, it comprises the additional step of pre-bending said ribbon at the end intended to first be fed through said opening. The step of pre-bending the ribbon contributes to make the ribbon strive towards the center
of the combined component (i.e. the inner curvature of the innermost cavity) . In other words, the pre-bending step reduces slack and makes it easier for the ribbon to be wound inside the bobbin, thus lowering the risk for the ribbon to break or get stuck because of jamming or too high friction or similar reasons.
According to another preferred embodiment of the method, it comprises the additional step of providing a part of said ribbon first being fed into the combined component, said part essentially corresponding to the first wound winding of said ribbon inside said combined component, on the side facing the inner curvature of the innermost hollow cavity of said combined component, with a layer having a low coefficient of friction for facilitating sliding of said ribbon while being wound inside said combined component. This low-friction layer primarily acts to reduce the obstacles related to stoppage or jamming of the ribbon that are often experienced when winding ribbons according to the prior art.
Still further, said layer is preferably provided by at least one of an adhesive tape having a first side with low coefficient of friction and a second side being adhesive, a coating with low coefficient of friction, and a fluid. All these surfaces are easily applicable and as such especially suitable for automated mass-production.
According to another preferred embodiment of the method, it comprises the additional step of arranging a flexible transmission element so that it is in continuous co-operation with the innermost winding of said ribbon, further facilitating sliding of said ribbon while being wound inside said combined component, thus forming the core. The flexible transmission element acts to improve
the filling degree of the ribbon inside the bobbin, either through transmitting a pulling force or a pushing force, or both. Further, said flexible transmission element is preferably comprised of at least one of a thread, a wire, a chain, an adhesive tape, a belt, a magnetic force, a roll device, and a meshing device. In any case, said flexible transmission element is reusable and easy to arrange, so that said flexible transmission element suitable for automated mass production. According to another preferred embodiment of the method, it comprises the additional step of arranging mediating means in connection to said ribbon for mediating co-operation between said flexible transmission element and said ribbon, said mediating means engaging with said flexible transmission element over a distance corresponding to at least a fraction of the innermost winding of said ribbon inside said combined component. Said mediating means is preferably comprised of at least one of an adhesive tape, an adhesive coating, a glue, a groove, and a meshing device. The mediating means is adapted to engage with both the ribbon and the flexible transmission element so that the movement of the flexible transmission element is transmitted to the ribbon so that it may more easily be wound inside the bobbin. The mediating means is so constituted that it handles large forces of friction.
In a preferred embodiment said mediating means comprises a from said ribbon protruding part of said layer. This refers, in one embodiment of the present invention, to the case where said layer is provided by an adhesive tape being fixed to the part of the ribbon intended to first be fed through the opening into the bobbin. Said tape is fixed so that a part of the adhesive
side of the tape protrudes outside of the ribbon, free to engage with the flexible transmission element, which in this case preferably could comprise a thread or wire. According to another preferred embodiment of the method, the step of feeding said ribbon of magnetic material through said opening further comprises rotating said combined component and stopping, essentially instantaneously, the rotation of said combined component together with said coil. A main advantage of this operation is the utilization of the principles for moment of inertia, by the effect of which the ribbon is forced to penetrate the opening into the bobbin and wind itself inside said bobbin in a single operation in a way that is easy to adapt for mass production purposes. According to another preferred embodiment of the method, the step of feeding said ribbon of magnetic material through said opening further comprises injecting a medium through said opening, thereby creating a variable gap between the outer curvature of the interior of said at least one first inner cavity in said combined component and leading said medium out from said combined component.
Said medium should primarily act to lower the forces of friction between the outer curvature of the interior cavity of the hollow bobbin and the ribbon when the latter is being wound inside the bobbin. In addition said medium has the advantage of helping to push the ribbon further inward, by help of compressive forces exerted onto the ribbon by the movement of the injected medium. Said medium is preferably comprised of at least one of a gas and a fluid. However, possibly, the medium could be a solid as well, such as a powder.
Further, in a preferred embodiment, said method for manufacture of toroidal transformers according to the present invention is performed in a magnetic field. Said magnetic field is preferably a variable magnetic field and presents two main advantages as compared to the prior art. Firstly, the magnetic field provides the windings of the ribbon with adhesive properties so that the windings stick to each other while the ribbon is being wound inside the bobbin. This contributes to a tightly formed core, having preferred electromagnetic features.
Secondly, the magnetic field can cause a turning force onto said ribbon, further facilitating the forming of the core. This may especially be the case if the magnetic field is provided with alternate strength in different sections along the bent bobbin and then rotating the toroid around the main axis.
According to another aspect of the present invention, it relates to a first bobbin for manufacture of toroidal transformers, characterised by said first bobbin essentially comprising at least two parallel flat elongated tongues, and said tongues being made by a flexible material and adapted to be bent. The main advantage of the first bobbin is that it allows for the winding of the coil to be performed using conventional winding machines. This is because said winding can be performed along a straight stretch, the bobbin being in a straight position, while traditionally, toroidal transformers are manufactured so that the winding of the coil is performed around a donut-shaped core, the disadvantages of which have been described earlier.
Furthermore, the bobbin is of a flexible material and adapted to be bent so that the bobbin ends can be brought towards each other. The flexible material could
for example be plastic material or rubber allowing the bobbin to be made in one piece by plastic moulding or similar methods. In one embodiment, said flexible material is a low-friction material. This especially an advantage for the interior cavity of the bobbin, making it easier to wind the ribbon inside the bobbin. Alternatively, the bobbin may be coated with a low- friction coating inside the hollow cavity.
The interior hollow cross-section of the bobbin is essentially of rectangular shape in order for the bobbin to be able to receive and accommodate the core material, as this core material comes in the form of a ribbon having a flattened rectangular-shaped cross-section, so that said ribbon, when being tightly wound inside the bobbin, builds up a core with an essentially rectangular- shaped cross-section.
According to another aspect of the present invention, it relates to a second bobbin for manufacture of toroidal transformers characterised by said second bobbin having at least one first inner cavity and at least one second inner cavity arranged around said at least one first inner cavity, said second bobbin being essentially circular segment-shaped, and said at least one first inner cavity having an essentially rectangular interior hollow cross-section. An advantage of the second bobbin according to the present invention is that it provides insulation sufficient to with-stand voltage stresses between the core and the coil windings in the toroidal transformer, since it remains part of the finally assembled toroidal transformer manufactured according to the method of the present invention. Another advantage of the second bobbin is that it provides a covering protection the coil windings in the toroidal
transformer against external wearing and stress, since it remains part of the finally assembled toroidal transformer manufactured according to the method of the present invention. In a preferred embodiment of the second bobbin, said at least one second inner cavity is wider at its inner curvature than at its outer curvature. For example, the general cross section of said at least one second inner cavity in said second bobbin could be shaped merely as a truncated triangle. One advantage with such a cross section shape is that it provides comparably more volume at the inner curvature than at the outer curvature, which permits the coil windings to gather at the inner curvature as said at least one first bobbin is being fed into said at least one second bobbin. It shall be noted that any shape of said cross section of said second bobbin that gives the same effect may be used, if desired.
According to another aspect of the present invention, it relates to a system for manufacture of toroidal transformers, the system comprising means for arranging a coil around the periphery of at least one first bobbin of elongated shape and of flexible material, means for providing at least one second bobbin, said second bobbin being essentially shaped as a circular segment and having at least one first inner cavity and at least one second inner cavity arranged around and along said at least one first inner cavity, means for feeding said at least one first bobbin, together with said coil, into said at least one second bobbin around said at least one first inner cavity, so that said coil is packed in said at least one second inner cavity, forming a component being essentially shaped as a circular segment,
wherein at least one of said component ends defines an opening, means for joining at least two of said components together, so that a combined component is formed, wherein at least one of said combined component ends defines an opening, and means for feeding a ribbon of magnetic material through said opening, so that said ribbon is being wound a required amount of tightly packed winding turns inside said at least one first inner cavity until essentially the whole at least one inner cavity of said combined component is filled, said ribbon thereby forming a core.
The advantages obtained with said system correspond to those of said method for manufacture of toroidal transformers according to the present invention and of said bobbin for manufacture of toroidal transformers according to the present invention, previously discussed.
According to another aspect of the present invention, it relates to a toroidal transformer manufactured by the above method. Such a toroidal transformer may be used in electrical equipment, such as adaptors .
BRIEF DESCRIPTION OF THE DRAWINGS
The features of the present invention will be more apparent upon reference to the drawings, wherein:
Fig 1 is a perspective drawing showing a first bobbin according to one embodiment of the present invention to be used for manufacturing of toroidal transformers, said first bobbin being shown in a mode where it is adapted for winding a coil around it;
Fig 2 is a perspective drawing showing the bobbin in Fig 1, with a coil wound around the bobbin;
Fig 3 is a perspective drawing of the first bobbin according to the present invention in a flexed mode;
Fig 4 is a perspective drawing showing a second bobbin according to one embodiment of the present invention to be used for manufacturing of toroidal transformers;
Fig 5a is a schematic perspective drawing showing the principle for how the first bobbin is intended to be fed into a receiving second bobbin; Fig 5b is a perspective drawing showing a first bobbin having a coil around it being fed into a receiving second bobbin;
Fig 6 is a schematic perspective drawing of one embodiment of a combined component, in the case where two components are joined together to form said combined component and where one of these components carries a primary winding and the other component carries a secondary winding;
Fig 7 is a schematic perspective drawing of the combined component in fig β, showing a ribbon of magnetic material being fed through an opening, thereby forming a core, and a flexible transmission element arranged so that said flexible transmission element co-operates with said ribbon, further facilitating the forming of said core;
Fig 8 is a flow chart corresponding to one embodiment of the method for manufacture of toroidal transformers according to the present invention; and
Fig 9 is a perspective drawing showing a toroidal transformer produced according to the method according to the present invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE
INVENTION
The invention will now, by way of example and for purposes of illustration only, be described further, with reference to the drawings.
Fig 1 is a perspective drawing showing a first bobbin 20 according to one embodiment of the present invention to be used for manufacturing of toroidal transformers, said first bobbin being shown in a mode where it is adapted for winding a coil around it.
Said first bobbin essentially comprises at least two parallel flat elongated tongues 22, 23.
The bobbin is of a flexible material and adapted to be bent. The flexible material could for example be plastic material or rubber allowing the bobbin to be made in one piece by plastic moulding or similar methods.
Said flexible material also provides the additional advantage of insulation sufficient to withstand voltage stresses between the core and the coil windings in the toroidal transformer, since said tongues remains a part of the finally assembled toroidal transformer manufactured according to the method of the present invention. In one embodiment, said flexible material is a low- friction material. This especially an advantage for the interior sides of said tongues, making it easier to feed said first bobbin into the second bobbin.
In one embodiment, shown in Fig 1, said tongues are of equal length. However, the tongues may have different lengths, especially such that the tongue intended to be fed into the second bobbin such that it is brought closest to the inner curvature of the second bobbin is
the shortest. This is in order to avoid that the innermost tongue is being crumpled up as it reaches further into the second bobbin, because the inner curvature distance is shorter than the outer curvature distance. However, in the embodiment of said first bobbin where said tongues are of equal length this crumpling may be accepted as the material making up the tongues are flexible and very thin, so that the tongues, when being crumpled up, only use a very small fraction of available space, hence not hampering the feeding process or the performance of the transformer.
Fig 2 is a perspective drawing showing the bobbin in Fig 1, with a coil wound around the bobbin. Most advantageously, said first bobbin allows for the winding of the coil to be performed using conventional winding machines in an automated operation. This is because said winding can, for example, be performed along a straight stretch, the bobbin being arranged in a straight position as in Fig 1 onto an elongated support structure (not shown), which is adapted to turn around its axis, while at the same time, during turning, a coil wire is wound around said first bobbin along the length of it, wholly or partly.
Fig 3 is a perspective drawing of the first bobbin according to the present invention in a flexed mode. This is essentially the shape the first bobbin will take on as it has been fed into the second bobbin, which is partly described above.
Fig 4 is a perspective drawing showing a second bobbin according to one embodiment of the present invention to be used for manufacturing of toroidal transformers .
The second bobbin for manufacture of toroidal transformers have least one first inner cavity and at least one second inner cavity arranged around and along said at least one first inner cavity. It is essentially shaped as a circular segment.
Preferably, said at least one first inner cavity has an essentially rectangular interior hollow cross-section in order for the component that is made up of at least one first bobbin and at least one second bobbin to be able to receive and accommodate the core material, as this core material comes in the form of a ribbon having a flattened rectangular-shaped cross-section, so that said ribbon, when being tightly wound inside the bobbin, builds up a core with an essentially rectangular-shaped cross-section.
In one embodiment said at least one second inner cavity is made of a low-friction material. This low- friction material makes it easier to wind the ribbon inside the combined component. Alternatively, said at least one second inner cavity may be coated with a low- friction coating.
In one embodiment, said at least one second inner cavity of said second bobbin is wider at its inner curvature than at its outer curvature. For example, the general cross section of said at least one second inner cavity in said second bobbin could be shaped merely as a truncated triangle. One advantage with such a cross section shape is that it provides comparably more volume at the inner curvature than at the outer curvature, which permits the coil windings to gather at the inner curvature as said at least one first bobbin is being fed into said at least one second bobbin. It shall be noted that any shape of said cross section of said second
bobbin that gives the same effect may be used, if desired.
Fig 5a is a schematic perspective drawing showing the principle for how the first bobbin is intended to be fed into a receiving second bobbin. In general, when being fed into the receiving second bobbin, said tongues are intended to run along the first inner cavity and to substantially bear against the outside surface of it during the feeding operation. Fig 5b is a perspective drawing showing a first bobbin having a coil around it being fed into a receiving second bobbin.
Fig 6 is a schematic perspective drawing of one embodiment of a combined component, in the case where two components are joined together to form said combined component and where one of these components carries a primary winding and the other component carries a secondary winding.
In another embodiment, however, said combined component may consist of only one section, comprising one first bobbin and one second bobbin, for which the primary and secondary windings are wound one on top of one another, both alongside the whole elongated, curved combined component. The ends of said first and second bobbins are preferably equipped with joining means (not shown) adapted for joining the ends together in one, single operation, thus securing the fastening of the bobbin ends to one another, so that a combined component may be formed. This allows for forming and ensuring a toroidal shape of said combined component and, hence, of said toroidal transformer. These joining means could, for example, comprise a clip device that is preformed during
plastic moulding of said first and second bobbins and thereby part of the bobbins themselves, or include the addition of an adhesive coating. Alternatively, the joining means could br accomplished by ultra sonic welding or by moulding the combined component or the complete transformator by dipping it in a sealing laquer. The joining means are adapted to be used during the ribbon feeding step, leaving a spacing between the bobbin ends through which the ribbon may be fed, and to be used for completely closing the toroidal ring, when the interior of the combined component is filled satisfactory.
Fig 7 is a schematic perspective drawing of the combined component in fig 6, showing a ribbon of magnetic material being fed through an opening, thereby forming a core, and a flexible transmission element arranged so that said flexible transmission element co-operates with said ribbon, further facilitating the forming of said core. A ribbon of magnetic material is being fed through an opening, so that said ribbon is being wound a required amount of tightly packed winding turns inside said combined component until essentially the whole innermost cavity of said combined component is filled, said ribbon thereby forming a core.
A flexible transmission element is arranged so that it co-operates with said ribbon, further facilitating the forming of said core, while being wound inside said bobbin. Said flexible transmission element acts to improve the filling degree of the ribbon inside the combined component, either through transmitting a pulling force or a pushing force, or both. Preferably, said flexible transmission element is in continuous co-
operation with the innermost ribbon winding of the core during the whole feeding step. This means that said flexible transmission element does not need to adjust for the increased core diameter as it is being wound inside the bobbin, meaning a simpler process as compared to, for example, US patent 4,779,812, in which the so called belt means are arranged to engage with the outermost core winding all the time during the winding process.
Further, said flexible transmission element most preferably comprises a thread or a wire. However, in other embodiments, the flexible transmission element is comprised of at least one of a chain, an adhesive tape, a belt, a magnetic force, a roll device, and a meshing device. In any case, said flexible transmission element is reusable and easy to arrange, so that said flexible transmission element suitable for automated mass production.
Mediating means may be arranged in connection to said ribbon for mediating co-operation between said flexible transmission element and said ribbon, said mediating means engaging with said flexible transmission element over a distance corresponding to at least a fraction of the innermost winding inside said combined component of said ribbon. The mediating means is adapted to engage with both the ribbon and the flexible transmission element so that the movement of the flexible transmission element is transmitted to the ribbon so that it may more easily be wound inside the combined component. The mediating means is so constituted that it can handle large forces of friction.
Said mediating means may comprise a from said ribbon protruding part of a specific layer. This refers especially to the case where said layer is provided by an
adhesive tape being fixed to the part of the ribbon intended to first be fed through the opening into the combined component. Said tape is fixed so that a part of the adhesive side of the tape protrudes outside of the ribbon, free to engage with the flexible transmission element, which in this case preferably could comprise a thread or wire. Hence, said mediating means most preferably comprises the adhesive side of an adhesive tape. However, other embodiments includes mediating means consisting of at least one of an adhesive coating, a glue, a groove, and a meshing device.
In one embodiment of said combined component according to the present invention, it comprises a slot set (not shown) comprising at least one slot, being arranged inside said bobbin for guiding a flexible transmission element. For example, said slot set may be helically arranged alongside the outer curvature of the at least one first inner cavity of said combined component. The slot set is adapted to receive the flexible transmission element and bring it in position before it is tightened and brought towards the mediating means. The slot set thus makes the application of the flexible transmission element easier.
Fig 8 is a flow chart corresponding to one specific embodiment of the method for manufacture of toroidal transformers according to the present invention. In the description below eventual numbered references, i.e. other than those representing the steps of the method, refer to the same numbered references as in the previous figures, Fig 1 to 7 and in the subsequent figure 9.
In step SlO, a coil is arranged around the periphery of at least one first bobbin of elongated shape and of
flexible material. The coil is arranged in place by the use of a conventional winding machine.
Thereafter, in step S20, at least one second bobbin is provided, said second bobbin being essentially shaped as a circular segment and having at least one first inner cavity and at least one second inner cavity arranged around and along said at least one first inner cavity.
The next main operation of the method, performed in step S30, is to feed said at least one first bobbin, together with said coil, into said at least one second bobbin around said at least one first inner cavity, so that said coil is packed in said at least one second inner cavity, forming a component being essentially shaped as a circular segment, wherein at least one of said component ends defines an opening.
Thereafter, in step 40, at least two of said components are joined together, so that a combined component is formed, wherein at least one of said combined component ends defines an opening. In step 50, a ribbon of magnetic material is fed through said opening, so that said ribbon is being wound a required amount of tightly packed winding turns inside said at least one first inner cavity until essentially the whole at least one inner cavity of said combined component is filled, said ribbon thereby forming a core.
However, in the particular embodiment of the present invention outlined in Fig 8, in connection to the feeding step S50, either before this step or after it, there is also performed a number of additional steps, S41 to S45, all of them in various ways preparing for and facilitating the feeding of the ribbon into the combined component and being discussed in more detail below. Further, as will be clarified in more detail later, steps
S51 to 56 also contribute in various ways to facilitating the feeding of the ribbon 0 into the combined component.
So, in step S41, after the combined component has been formed, the ribbon is first pre-bent at the end of it intended to first be fed through said opening.
The pre-bending operation is preferably performed by a roll device, arranged outside said opening, the principles of which is not shown. Said roll device also serves as a pushing device, pushing the ribbon towards and through said opening into the combined component, further facilitating the winding of the core material inside the combined component. Due to the pre-bending operation the ribbon is better adapted for striving towards the center of the combined component (i.e. the inner curvature of the innermost cavity) , while being wound. In other words, the pre-bending step reduces slack and makes it easier for the ribbon to be wound inside the bobbin, thus lowering the risk for the ribbon to break or get stuck because of jamming or too high friction or similar reasons.
Thereafter, in step S42, the particular part of said ribbon that is first being fed into the combined component, where said part essentially corresponds to the first wound winding inside said combined component of said ribbon on the side of said ribbon that faces the inner curvature of the innermost hollow cavity of the combined component, is provided with a layer having a low coefficient of friction in order to facilitate the sliding of said ribbon when it is wound inside said bobbin.
By this, obstacles related to stoppage or jamming of the ribbon that otherwise could be are reduced. Furthermore, the layer contributes to transform a
torsional force into a gripping force, which leads to that it is no longer necessary to apply a welding joint to the ribbon in order to fix the innermost winding of the ribbon, as in, for example, US patent 4,779,812, which, by the way, would not be appropriate or even possible with the method according to the present invention, because of the closed structural configuration of the combined component with the coil wound inside it. Further, said part of said ribbon first being fed into the bobbin preferably corresponds essentially to the first wound winding inside said combined component of said ribbon. It is essentially the innermost winding of the ribbon that directly and actively is in close contact with the combined component. To apply said low-friction surface to additional windings could in fact counteract the continuous tightening of the windings inside the combined component, so that there is a risk for jamming of the ribbon or that the ribbon is not wound tight enough. Still further, in a preferred embodiment said layer is provided by an adhesive tape having a first side with low coefficient of friction and a second side being adhesive. In other embodiments, however, said layer could comprise at least one of a coating with low coefficient of friction and a fluid.
In step S43, a flexible transmission element is arranged so that it can be in continuous co-operation with the innermost winding of said ribbon, thereby further facilitating the sliding of the ribbon while being wound inside said combined component and contributing to forming the core.
In step S44, mediating means are arranged in connection to said ribbon for mediating co-operation
between said flexible transmission element and said ribbon, said mediating means engaging with said flexible transmission element over a distance corresponding to at least a fraction of the innermost winding inside said combined component of said ribbon. The mediating means is adapted to engage with both the ribbon and the flexible transmission element so that the movement of the flexible transmission element is transmitted to the ribbon so that it may more easily be wound inside the combined component. The mediating means is so constituted that it can handle large forces of friction.
In a preferred embodiment of the present invention, said mediating means comprises a from said ribbon protruding part of said layer provided in step 42. This refers especially to the case where said layer is provided by an adhesive tape being fixed to the part of the ribbon intended to first be fed through the opening into the combined component. Said tape is fixed so that a part of the adhesive side of the tape protrudes outside of the ribbon, free to engage with the flexible transmission element, which in this case preferably could comprise a thread or wire. Hence, said mediating means most preferably comprises the adhesive side of an adhesive tape. However, other embodiments includes mediating means consisting of at least one of an adhesive coating, a glue, a groove, and a meshing device.
In the particular embodiment shown in Fig 8, the method is being performed in a magnetic field, which is provided in S45. The magnetic field (not shown) is preferably a variable magnetic field, provided by a device for producing magnetic fields and the presence of which presents at least two main advantages as compared to the prior art. Firstly, the magnetic field provides
the windings of the ribbon with adhesive properties so that the windings stick to each other while the ribbon is being wound inside the combined component. This contributes to a tightly formed core, having preferred electromagnetic features. Secondly, the magnetic field causes a turning force onto said ribbon, further facilitating the forming of the core. This may especially be the case if the magnetic field is provided with alternate strength in different sections along the combined component and then rotating the toroid around the main axis.
Returning again to fig 8, in step S51, a medium is injected through said opening, so that a variable gap is created between the outer curvature of the interior of said combined component, and said ribbon.
In step S52, the medium injected in step S51 is lead out from the combined component. In fact, steps S51 and S52 are performed in parallel and more or less continuously during the whole feeding step. Said medium act to lower the forces of friction between the outer curvature of the innermost cavity of the combined component and the ribbon when the latter is being wound inside the combined component. In addition, said medium has the advantage of helping to push the ribbon further inward, by help of compressive forces exerted onto the ribbon by the movement of the injected medium. Said medium is preferably comprised of at least one of a gas and a fluid. However, possibly, the medium could be a solid as well, such as a powder. In step S53, the ribbon 40 is cut at a desired length after having been fed through opening into the combined component, so that a core has been formed.
In step 54, the flexible transmission element that was arranged in step S53, is removed.
In step 55, the combined component is arranged on a rotation device and rotated at high speed. Thereafter, suddenly, in step S56, the rotation of said combined component s stopped, essentially instantaneously. Since these operations (i.e. steps S5 and S5) are being performed in an uninterrupted sequence, one can profit from the principles for moment of inertia, by the effect of which the ribbon is forced to penetrate the opening into the combined component and wind itself inside said combined component in a single operation in a way that is easy to adapt for mass production purposes.
Preferably, the rotation and stopping steps are being performed after the step of cutting the ribbon at a desired length after having fed the ribbon through the opening, so that the part of the ribbon still remaining outside of the combined component can be brought inside the combined component. This allows for the combined component to be completely filled with the core material without leaving unused space inside the combined component, something that would lower the efficiency of the toroidal transformer. Furthermore, if a part of the ribbon would protrude from the opening of the combined component outside of the coil windings, the performance of the transformer would be unsatisfactory and insulating requirements would risk not to be met.
In this embodiment, said rotation device comprises a holder (not shown) onto which the combined component is arranged. Said holder could, for example, essentially consist of a grommet, which can be gradually filled with a medium, such as pressurised air, for fixing the combined component (and emptied of the same, for
releasing the combined component from the holder) . Said holder is adapted to rotate at high speed and to be stopped essentially instantaneously on command thereof. Fig 9, finally, is a perspective drawing showing a toroidal transformer produced according to the method according to the present invention.
It should be pointed out that the present invention is not limited to the realizations described above. The foregoing discussion merely describes exemplary embodiments of the present invention. The skilled man will readily recognize that various changes and modifications may be made without departing from the spirit of the invention, as defined in the claims.
For example, not all of the steps described above need to be performed in order for considering the method to be performed according to the present invention. Any of the other steps can, wholly or partly, be left out or modified. Further, the steps need not to be performed according to the above chronology, rather they can be performed in various combinations after each other.
Another example of a possible modification is that the winding of the coil around the bobbin, besides being performed by conventional winding machines, also may be performed by hand power. Even though an object of the present invention is to provide a method and a system for manufacture of toroidal transformers, having properties superior for automated mass production, which is especially adapted for manufacture of small transformers that are used in ordinary electrical equipment, the method, system and other aspects of the present invention are very suitable also for manufacture of larger transformers.
Claims
1. Method for manufacture of toroidal transformers, the method comprising the steps of: arranging a coil around the periphery of at least one first bobbin of elongated shape and of flexible material; providing at least one second bobbin, said second bobbin being essentially shaped as a circular segment and having at least one first inner cavity and at least one second inner cavity arranged around and along said at least one first inner cavity, feeding said at least one first bobbin, together with said coil, into said at least one second bobbin around said at least one first inner cavity, so that said coil is packed in said at least one second inner cavity, forming a component being essentially shaped as a circular segment, wherein at least one of said component ends defines an opening, joining at least two of said components together, so that a combined component is formed, wherein at least one of said combined component ends defines an opening, and feeding a ribbon of magnetic material through said opening, so that said ribbon is being wound a required amount of tightly packed winding turns inside said at least one first inner cavity until essentially the whole at least one inner cavity of said combined component is filled, said ribbon thereby forming a core.
2. Method according to claims 1, comprising the additional step of: pre-bending said ribbon at the end of said ribbon intended to first be fed through said opening.
3. Method according to any one of claims 1 or 2, comprising the additional step of: providing a part of said ribbon first being fed into the combined component, said part essentially corresponding to the first wound winding of said ribbon inside said combined component, on the side facing the inner curvature of the innermost hollow cavity of said combined component, with a layer having a low coefficient of friction for facilitating sliding of said ribbon while being wound inside said combined component.
4. Method according to claim 3, wherein said layer is provided by at least one of an adhesive tape having a first side with low coefficient of friction and a second side being adhesive, a coating with low coefficient of friction, and a fluid.
5. Method according to any one of claims 1 to 4, comprising the additional step of: arranging a flexible transmission element so that it is in continuous co-operation with the innermost winding of said ribbon, further facilitating sliding of said ribbon while being wound inside said combined component, thus forming the core.
6. Method according to any one of claims 4 or 5, comprising the additional step of: arranging mediating means in connection to said ribbon for mediating co-operation between said flexible transmission element and said ribbon, said mediating means engaging with said flexible transmission element over a distance corresponding to at least a fraction of the innermost winding of said ribbon inside said combined component.
7. Method according to claim 6, wherein said mediating means comprises a from said ribbon protruding part of said layer.
8. Method according to any one of claims 1 to 7, wherein the step of feeding said ribbon of magnetic material through said opening further comprises: rotating said combined component; and stopping, essentially instantaneously, the rotation of said combined component together with said coil.
9. Method according to any one of claims 1 to 8, wherein the step of feeding said ribbon of magnetic material through said opening further comprises: injecting a medium through said opening, thereby creating a variable gap between the outer curvature of the interior of said at least one first inner cavity in said combined component; and leading said medium out from said combined component (35) .
10. Method according to any one of claims 1 to 9, wherein said method is performed in a magnetic field.
11. First bobbin for manufacture of toroidal transformers, c h a r a c t e r i s e d b y : said first bobbin essentially comprising at least two parallel flat elongated tongues, and said tongues being made by a flexible material and adapted to be bent.
12. Second bobbin for manufacture of toroidal transformers, c h a r a c t e r i s e d b y : said second bobbin having at least one first inner cavity and at least one second inner cavity arranged around and along said at least one first inner cavity, said second bobbin being essentially shaped as a circular segment, and said at least one first inner cavity having an essentially rectangular interior hollow cross-section.
13. Second bobbin according to claim 12, wherein said at least one second inner cavity is wider at its inner curvature than at its outer curvature.
14. System for manufacture of toroidal transformers, the system comprising: means for arranging a coil around the periphery of at least one first bobbin of elongated shape and of flexible material; means for providing at least one second bobbin, said second bobbin being essentially shaped as a circular segment and having at least one first inner cavity and at least one second inner cavity arranged around and along said at least one first inner cavity, feeding said at least one first bobbin, together with said coil, into said at least one second bobbin around said at least one first inner cavity, so that said coil is packed in said at least one second inner cavity, forming a component being essentially shaped as a circular segment, wherein at least one of said component ends defines an opening, means for joining at least two of said components together, so that a combined component is formed, wherein at least one of said combined component ends defines an opening, and means for feeding a ribbon of magnetic material through said opening, so that said ribbon is being wound a required amount of tightly packed winding turns inside said at least one first inner cavity until essentially the whole at least one inner cavity of said combined component is filled, said ribbon thereby forming a core.
15. Toroidal transformer manufactured by said method for manufacture of toroidal transformers, according to any one of claims 1 to 11.
16. Use of a toroidal transformer according to claim 15 in electrical equipment, such as adaptors.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE0403215A SE528356C2 (en) | 2004-12-30 | 2004-12-30 | Method for manufacturing toroidal transformers, first coil, second coil, system, toroidal transformer and use |
| SE0403215-7 | 2004-12-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2006071182A1 true WO2006071182A1 (en) | 2006-07-06 |
Family
ID=34102157
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/SE2005/002024 WO2006071182A1 (en) | 2004-12-30 | 2005-12-23 | Improved manufacture of toroidal transformers |
Country Status (3)
| Country | Link |
|---|---|
| CN (1) | CN101095204A (en) |
| SE (1) | SE528356C2 (en) |
| WO (1) | WO2006071182A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20190122813A1 (en) * | 2017-10-23 | 2019-04-25 | Schweitzer Engineering Laboratories, Inc. | Current transformer with flexible secondary winding |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4779812A (en) * | 1982-01-06 | 1988-10-25 | Kuhlman Corporation | Toroidal electrical transformer and method of producing same |
| WO1998010449A1 (en) * | 1996-09-05 | 1998-03-12 | Vacuumschmelze Gmbh | Method and device for the manufacture of an inductive component |
-
2004
- 2004-12-30 SE SE0403215A patent/SE528356C2/en not_active IP Right Cessation
-
2005
- 2005-12-23 CN CNA2005800454836A patent/CN101095204A/en active Pending
- 2005-12-23 WO PCT/SE2005/002024 patent/WO2006071182A1/en active Application Filing
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4779812A (en) * | 1982-01-06 | 1988-10-25 | Kuhlman Corporation | Toroidal electrical transformer and method of producing same |
| WO1998010449A1 (en) * | 1996-09-05 | 1998-03-12 | Vacuumschmelze Gmbh | Method and device for the manufacture of an inductive component |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20190122813A1 (en) * | 2017-10-23 | 2019-04-25 | Schweitzer Engineering Laboratories, Inc. | Current transformer with flexible secondary winding |
| US10777349B2 (en) * | 2017-10-23 | 2020-09-15 | Schweitzer Engineering Laboratories, Inc. | Current transformer with flexible secondary winding |
Also Published As
| Publication number | Publication date |
|---|---|
| SE0403215D0 (en) | 2004-12-30 |
| SE528356C2 (en) | 2006-10-24 |
| SE0403215L (en) | 2006-07-01 |
| CN101095204A (en) | 2007-12-26 |
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