Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
1998-09-17
2001-08-14
Lorin, Francis J. (Department: 1775)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S397000, C174S1200SR, C174S1210SR, C310S179000
Reexamination Certificate
active
06274240
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to insulated electrical conductors, and, in particular, to a method for forming insulated magnet wire and to a coil constructed from such insulated magnet wire.
Insulated magnet wire is typically used to form coils that create magnetic fields within electrical devices such as motors and transformers. In order to provide adequately strong magnetic fields, the coils are frequently manufactured with a multitude of overlaying layers of spirally wound wire. To ensure optimum operation of the coil, it is highly desireable that the electric current within the wire be prevented from jumping between successive windings (i.e. turn-to-turn jumping) in a coil layer, as well as prevented from jumping between successive layers (i.e. layer-to-layer) of the coil windings.
Overall, prior attempts to overcome layer-to-layer electrical current jumping have provided a workable degree of success. Such attempts frequently involved wrapping a sheet of electrically insulative material between the successive winding layers during coil manufacture. However, an assortment of existing techniques for preventing turn-to-turn electrical current jumping, while to a certain extent offering functional results, suffer from a variety of shortcomings which detract from their desirability.
For example, one technique previously employed to insulate a magnet wire is to coat the entire wire with an insulating resin or enamel. However, resin wire coatings alone are frequently susceptible to nicks or scratches during coil formation and/or use which compromises the insulating function of the coating.
An assortment of other techniques completely or partially wrap the wire with tapes or webs made of paper which absorbs oil that acts as an electrical insulator when used in an oil-filled transformer, or with tapes or webs made of insulating material, such as woven glass or NOMEX®, which are less susceptible to nicks. However, due to the relatively high cost of the tapes such as made from NOMEX®, these techniques, especially if excessive amounts of tape are utilized, make the wire product expensive. For example, one prior art technique spirally wraps the wire in a first direction with a first tape and then helically or spirally wraps the wire in a second direction with a second tape. While the second wrap may serve to stagger the tape seams such that the magnet wire is less likely to be exposed when the wrapped magnet wire is bent into a proper coil arrangement, the cost of multiple tape layers may be prohibitive for many applications.
Another known cigarette wrap type technique entails extruding onto the full circumference of a round conductor wire a heat activated adhesive. An electrically insulating wrap is then longitudinally wrapped around the entire adhesive coated wire to provide dielectric properties absent in the adhesive. A shortcoming of this technique is that because a complete wrapping of the wire is required to ensure that the wire, when eventually wound into a coil, is properly insulated, large amounts of expensive insulating tape are required.
U.S. Pat. No. 5,254,806 discloses a wire wrapping method that uses pressure sensitive adhesive on an insulating tape to wrap a magnet wire. The adhesive is covered by a release paper which is stripped from the tape immediately prior to application of the tape to the wire. A disadvantage of this method is the inconvenience of handling the release strip during wire formation. A further disadvantage is that the adhesive is flowed onto the tape and then covered with the release strip in a secondary process frequently performed by an outside supplier. The need for the precoated tape may be a source of delays and may further increase the cost of the manufacturing process.
In another method for insulating wire disclosed in U.S. Pat. No. 4,159,920, a binder coated tape is applied to a heated conductor wire. Besides requiring that heating units be provided to heat the wire before and possibly after tape application, this method further suffers from the need to use tape precoated with an adhesive, which as described above may increase the manufacturing costs of the wire.
In order to provide a magnet wire coil which utilizes less wrapped wire, one prior art design traversely winds a pair of magnet wires to form a layer. One wire of the pair is completely wrapped in insulation while the other wire is not provided with insulation. For this design, the turn to turn insulation is intended to be achieved by the insulation of the wrapped wire interposed between successive windings of the bare wire. This coil design may complicate manufacture as two wires must be handled during coil assembly.
Thus, it would be desireable to provide an insulated magnet wire which can be readily manufactured and which can serve to provide adequate insulation for a coil without wasting valuable raw materials.
SUMMARY OF THE INVENTION
The present invention provides a method of forming electrically insulated magnet wire that streamlines the manufacturing process by its steps of applying adhesive to a passing insulating tape and then promptly adhering the coated tape to a passing wire. The inefficient prior art methods which first create or procure a prefabricated adhesive coated tape, and then reactivate the adhesive during wire wrapping have been improved upon while still allowing for partial, longitudinal wire wrapping.
In one form thereof, the present invention provides a method of forming an electrically insulated wire and includes the step of providing a supply of tape and a supply of heat activated adhesive, wherein at least one of the tape and adhesive provides a means for electrical insulation, and wherein when the tape comprises the means for electrical insulation the tape comprises at least one of a material of construction having an electrically insulative property and a material of construction adapted to absorb an electrically insulating material in an environment in which the electrically insulated wire is to be employed. The method also involves moving a conductor wire along a first path, and moving the tape along a second path, wherein the first and second paths converge to a mounting zone whereat the tape is mounted to the wire. The method further involves heating the adhesive to an adhering state, applying the adhesive to the tape in the adhering state at a location along the second path, and, at the mounting zone, adhering the tape to the wire with the adhesive in the adhering state to provide at least a portion of the periphery of the wire with an electrically insulative wrap.
In another form thereof, the present invention provides a method of forming an electrically insulated magnet wire and includes the steps of feeding a supply of conductor wire along a first path, feeding a flexible electrical insulation tape along a second path, wherein the first and second paths converge to a mounting zone whereat the tape is mounted to the wire, and heating a heat activated adhesive with dielectric properties to an adhering state. The method further involves applying the adhesive to the tape in the adhering state at a location along the second path prior to the mounting zone, and, at the mounting zone, adhering the tape to the wire with the adhesive in the adhering state to provide a longitudinal wrap along the wire, wherein the longitudinal wrap covers only a portion of the periphery of the wire.
One advantage of the present invention is that an insulated magnet wire can be produced without the use of release strips or prefabricated, adhesive coated insulating tapes.
Another advantage of the present invention is that a magnet wire can be longitudinally and partially wrapped in a convenient, and raw materials efficient, manner.
Another advantage of the present invention is that a partial wrapping of a magnet wire with an insulating resin may be performed.
Still another advantage of the present invention is that a magnet wire coil can be provided with adequate turn-to-turn electrical insulation without the magnet wire insulation being wrapped around
Alconex Specialty Products, Inc.
Baker & Daniels
Lorin Francis J.
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