Patent Grant
6933828
The present invention relates to protection devices and, more particularly, to devices and methods for protecting windings.
A variety of different products are known which require wrapping of windings around a core member having an opening therein. Example of such products include electromagnetic sensor equipment and electrical transformers. Such products typically include a cylindrical shaped metal core having electrically conductive wires wrapped around the core.
As the conductive core and the electrically conductive wires typically must be isolated, the wires in such products are often coated, for example, with a varnish or other insulating coating. However, it is often desirable, for manufacturing and/or performance reasons, to utilize a sharp edged core with right angle interfaces at each of the outer and inner corner surfaces of the core around which the wires must be wrapped. These edges may cut into the wiring and undesirably introduce an electrically conductive path between the core and the wrapped wiring. Accordingly, various approaches have been proposed for protecting the wrapped wiring.
In one prior art approach, a non-conductive paper is placed around the core before the wire is wrapped around the core. For example, sheet cardboard may be cut to provide two circular portions with outer diameter and inner diameter values selected to correspond to the end faces of the core. A first and second rectangular strip are also cut with lengths corresponding to the circumference of the core at the respective outer diameter of the core and the diameter of the opening in the center of the core through which the wires will pass and a width corresponding to the width of the core between its end faces. These four pieces are then positioned around the outer surface of the core and taped in place. The wire (typically ranging from about 8 AWG to about 32 AWG) may then generally be safely wrapped around the core without damaging the insulating coating (for example, varnish) of the wire. However, due, in part, to the variety of different diameters (typically about 4 inches (10.16 centimeters) to about 44 inches (111.76 centimeters)) and widths (typically about 1.25 inches (3.175 centimeters) to about 8.5 inches (21.59 centimeters)) of the cores, a great deal of waste is typically encountered using the non-conductive paper wrapping. For example, the cut out of the center of the rings for the end pieces must, typically, be scrapped along with the outer portions of the material after the end pieces are cut out. The taping operation provides additional expense in materials and labor as well.
An alternative approach has been proposed in which a 90 degree plastic extrusion with two equal length sides is placed over the corners of the core. However, a problem with this approach is the tendency of the material to have uneven sides due to the wrapping of the extrusion around the circumference of the core, particularly on the edges of the inner opening of the core. This problem may be particularly acute for smaller diameter cores. In addition, an overlap of the ends of the extrusion to complete the wrap of the circumference without leaving any exposed sharp edges would result in an undesirable bump on the surface which, like the rippling caused by the wrapping of the extrusion into a circular configuration, could adversely affect performance of the finished electromagnetic product.
According to embodiments of the present invention, electromagnetic devices are provided including an electrically conductive core having an inner diameter defining an opening therethrough and an outer diameter, the core having sharp edges extending circumferentially around the inner diameter and around the outer diameter thereof. A plurality of polymeric protection members are wrapped circumferentially around the core and positioned adjacent the sharp edges of the core. An adhesive layer is positioned between the protection members and the core connecting the protection members to the core. A coated wire is wrapped around the core so as to be magnetically coupled thereto and around the polymeric protection members so as to be displaced from the sharp edges of the core.
In further embodiments of the present invention, electromagnetic devices are provided including an electrically conductive core having an inner diameter defining an opening therethrough and an outer diameter, the core having sharp edges extending circumferentially around the inner diameter and around the outer diameter thereof. A plurality of polymeric protection members are wrapped circumferentially around the core and positioned adjacent the sharp edges of the core. The protection members have at least one short leg positioned adjacent at least one end of the core. The short leg has a length selected to provide a substantially flat surface on the end of the core when the protection members are wrapped around the core. A coated wire is wrapped around the core so as to be magnetically coupled thereto and around the polymeric protection members so as to be displaced from the sharp edges of the core.
In other embodiments of the present invention, the protection members are L-shaped strips having a short leg positioned adjacent an end of the core and a long leg positioned adjacent a circumferential face of the core. The short leg has a length selected to provide a substantially flat surface on the end of the core. In alternative embodiments of the present invention, the protection members are channel shaped members having a width at least equal to a width of the core and a first and second leg at opposite sides thereof and a channel portion extending therebetween. The channel shaped members are wrapped around the core so as to position the first leg adjacent a first end of the core and the second leg adjacent an opposite end of the core with a circumferential face of the core positioned in the channel shaped member.
In further embodiments of the present invention, the adhesive layer is positioned adjacent the short leg of the protection members. The long leg and/or channel portion of the protection members may directly contact the core without an adhesive layer therebetween. The protection members may further include a first end and a second end thereof, the first end and second end defining mating angles at an overlapping region of the protection members when the protection members are wrapped around the core so as to extend around the entirety of one of the sharp edges of the core without a bump discontinuity at the overlapping region. The mating angles may be between about 15 degrees and 75 degrees and, in further embodiments, may be 45 degree angles.
In other embodiments of the present invention, the outer diameter of the core is at least about 5 centimeters (3 inches) and the first and second leg each have a length of less than about 0.32 centimeters (0.125 inches). In further embodiments, the outer diameter of the core is at least about 22 centimeters (9 inches) and the first and second leg each have a length of less than about 1 centimeter (0.375 inches).
In further embodiments of the present invention, the protection members are a crosslinked polymeric material having a dielectric strength selected to limit breakdown of the protection members by magnetic fields generated around the core. The dielectric strength may be at least about 200 volts/centimeter. The polymeric material may be stable at 150 degrees Centigrade for at least about 100 hours. The crosslinked polymeric material may be either medium or high density polyethylene.
In a further aspect of the present invention, protection members are provided for a device including a sharp-edged core and elongate members wrapped therearound. The protection member is an L-shaped strip having a short leg configured to be positioned adjacent an end of the core, abutting a circumferentially extending sharp edge of the core, and a long leg extending substantially transversely from the short leg so as to be positioned adjacent a circumferential face of the core. The short leg has a length selected to provide a substantially flat surface on the end of the core when wrapped around the core. Alternatively, the protection members may be channel shaped members having a width at least equal to a width of the core and a first and second leg at opposite sides thereof and a channel portion extending therebetween, the channel shaped members being configured to be wrapped around the core so as to position the first leg adjacent a first end of the core and the second leg adjacent an opposite end of the core with a circumferential face of the core positioned in the channel shaped member. The first and second legs each have a length selected to provide a substantially flat surface on the end of the core when wrapped around the core. The device may be an electromagnetic device and the elongate members may be wires having an insulating coating thereon.
In yet another aspect of the present invention, methods are provided for assembling an electromagnetic device including a sharp-edged core and at least one wire wrapped therearound. Polymeric protection members are placed around sharp edges of the core extending circumferentially around an inner diameter and around an outer diameter of the core. The protection members have a short leg positioned adjacent an end of the core. The short leg has a length selected to provide a substantially flat surface on the end of the core when the protection members are wrapped around the core. A wire is wrapped around the core so as to be magnetically coupled thereto and around the polymeric protection members so as to be displaced from the sharp edges of the core. An adhesive layer may be placed on an inner surface of the polymeric protection members to secure the polymeric protection members to the core.
In another aspect of the present invention, methods are provided for fabricating a polymeric protection member for a device including a core having circumferentially extending sharp edges around an inner diameter and around an outer diameter thereof around which elongate members are wrapped. A circumferential length of one of the sharp edges is determined. A length of a polymeric protection strip stock is measured out corresponding to the determined circumferential length. The polymeric protection strip stock is cut to the measured length to provide the protection member. More particularly, the polymeric protection strip stock is cut at an angle selected to define mating angles at an overlapping region of the protection member when the cut protection member is wrapped around the core so as to extend around the entirety of one of the sharp edges of the core without a bump discontinuity at the overlapping region. The angle may be between about 15 degrees and about 75 degrees. The polymeric protection strip stock may have at least one short leg configured to be positioned adjacent at least one end of the core. The short leg may have a length selected to provide a substantially flat surface on the end of the core when the polymeric protection member is wrapped around the core.
In further embodiments of the present invention, electromagnetic devices are provided including an electrically conductive core having at least one circumferentially extending sharp edge. At least one polymeric protection member is wrapped circumferentially around the core and positioned adjacent the at least one circumferentially extending sharp edge of the core. The at least one protection member further includes a first end and a second end thereof, the first end and second end defining mating angles at an overlapping region of the at least one protection member when the protection member is wrapped around the core so as to extend around the entirety of the at least one circumferentially extending sharp edge of the core without a bump discontinuity at the overlapping region. An insulated wire is wrapped around the core so as to be magnetically coupled thereto and around the at least one polymeric protection member so as to be displaced from the at least one circumferentially extending sharp edge of the core. In such embodiments including mating angles, the protection member(s) may comprise L-shaped members with a short leg positioned adjacent an end face of the core and a long leg extending substantially transversely therefrom, channel shaped members, L-shaped members with the long leg positioned adjacent the end face of the core and/or angled members with equal length legs.
Objects of the present invention will be appreciated by those of ordinary skill in the art from a reading of the figures and the detailed description of the preferred embodiments which follow, such description being merely illustrative of the present invention.
The accompanying drawings which form a part of the specification, illustrate key embodiments of the present invention. The drawings and description together serve to fully explain the invention. In the drawings,
The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements throughout. The terms “upwardly”, “downwardly”, “vertical”, “horizontal” and the like are used herein for the purpose of explanation only.
Referring now to
As shown in
An electromagnetic device 200 including a core such as that shown in
Referring now to the illustration of
Referring now to
As shown for the embodiments of
The respective ends of the protection member 355 define mating angles which will overlap when the protection member 355 is fully wrapped around the core 352 so as to extend the protection member 355 around the entirety of the sharp edges 370, 370′ without a bump discontinuity being presented in the overlapping region. For the embodiment illustrated in
The protection member 305 or 355 may be provided as an extruded plastic profile. As will be further described herein, the extruded profile can also have one surface coated with a high tack adhesive or other mastic bonding substrate to provide an adhesive layer for coupling the protection member 305, 355 to the core. Such an extruded profile may be supplied as a continuous wrap reeled, for example, on a large spool.
For electromagnetic devices, such as sensors or transformers, a broad range of outer diameters for the core may be encountered. It is preferred that the legs 309, 359, 359′ adjacent the end faces of the core in such devices have lengths selected to provide a substantially flat surface on the ends of the core when the protection members 305, 355 are wrapped around the core. More particularly, an excessive length of the legs 309, 359, 359′, relative to the bend radius introduced based on the diameter of the core where the protection member is utilized, may cause a ripping of the leg 309, 359, 359′ along the ends which may be undesirable for the performance of the resulting device. In various embodiments of the present invention, where the outer diameter (i e., the diameter at which the protection member is to be applied) is at least about 5 centimeters (3 inches), the short leg has a length of less than about 0.32 centimeters (0.125 inches). In further embodiments, the outer diameter of the core is at least about 22 centimeters (9 inches) and the short leg has a length of less than about 2 centimeters (¾ inches) and, more preferably, less than about 1 centimeter (0.375 inches). The protection member may have a material thickness of between about 1 millimeter and about 3 millimeters.
The adhesive layer between the protection member 305, 355 and the core 302, 352 may be positioned adjacent the short leg 309, 359, 359′ of the protection members 305, 355. The long leg 307 of the protection member 305 and/or the channel portion 357 of the protection member 355 may directly contact the core without an adhesive layer therebetween in various embodiments of the present invention.
The material used in the forming of the protection members 305, 355 may be a crosslinked polymeric material. The crosslinked polymeric material preferably has a dielectric strength selected to limit breakdown of the protection members by magnetic fields generated around the core. The dielectric strength may, for example, be at least about 200 volts/centimeter and, more preferably, may be about 217 volts/centimeter with a material thickness of 1.27 millimeters for the protection members. The crosslinked polymeric material may be a medium or high density polyethylene material or other suitable material.
Further material properties for the protection members 305, 355 which may be beneficial in various applications include heat stability at 150 degrees Centigrade for at least about 100 hours and, more preferably, for about 168 hours. The thermal endurance of the polymeric material may be about 20,000 hours at 105 degrees Centigrade. The abrasion resistance for the polymeric crosslinked material may be 20% maximum material loss after 1,000 cycles at 2068 grams. The crosslinked polymeric material may further have a low temperature impact resistance down to about −20 degrees Centigrade.
Referring now to the illustration of
Substantially L-shaped protection members in accordance with various embodiments of the present invention are further illustrated in
Referring now to
A section of strip stock defining a protection member having a channel or rail shape according to embodiments of the present invention, such as those illustrated in
Referring now to
Referring now to
In various embodiments, the protection members may be applied directly to the core by resting an inner surface thereof against the sharp edges defined in a perimeter of the core. Each of the protection members may be cut to a length that matches the circumference of the inner or outer diameter to be protected before applying the protective strips to the sharp edges. In further embodiments, an adhesive layer may be placed on an inner surface of the polymeric protection members before placing them on the core so as to secure the protection members to the core. Alternatively, or in addition to the adhesive layer, a tape, such as a glass tape, may be wrapped around the protection members before the wire is wrapped around the core.
Referring now to
Operations begin by determining a circumferential length of one of the sharp edges of the core (block 900). A length of a polymeric protection strip stock corresponding to the determined circumferential length is measured out (block 910). The polymeric protection strip stock is cut to the measured length to provide the protection member (block 920). The polymeric protection strip stock is cut at an angle selected to define mating angles at an overlapping region of the protection member when the cut protection member is wrapped around the core. This may provide for a protection member which extends around the entirety of one of the sharp edges of the core without a bump discontinuity being introduced at the overlapping region where the ends of the polymeric protection strip stock meet. An apparatus such as that illustrated in
The foregoing is illustrative of the present invention and is not to be construed as limiting thereof. Although a few exemplary embodiments of this invention have been described, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Therefore, it is to be understood that the foregoing is illustrative of the present invention and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed embodiments, as well as other embodiments, are intended to be included within the scope of the appended claims. The invention is defined by the following claims, with equivalents of the claims to be included therein.
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| Number | Date | Country | |
|---|---|---|---|
| 20020190836 A1 | Dec 2002 | US |
