Inductor devices – With supporting and/or spacing means between coil and core – Preformed insulation between coil and core
Reexamination Certificate
1998-09-21
2001-01-30
Gellner, Michael L. (Department: 2832)
Inductor devices
With supporting and/or spacing means between coil and core
Preformed insulation between coil and core
C336S192000, C336S208000
Reexamination Certificate
active
06181230
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to electromechanical utility watthour meters. More particularly, the present invention relates to voltage coils for use in such meters.
BACKGROUND OF THE INVENTION
A voltage coil is an essential component in the electromagnet section of an electromechanical utility watthour meter. Voltage coils typically comprise three primary elements: a bobbin composed of an electrically inert material, wire capable of generating a magnetic field, and isolated terminal or wire ends. A voltage coil is also encapsulated prior to final testing. The manufacture of conventional voltage coils is labor intensive and these voltage coils are typically not able to handle large voltages; e.g., those on the order of about 8,000 volts.
FIG. 1A
shows a top view of a conventional voltage coil.
FIG. 1B
shows a bottom view (without attached terminals) and
FIG. 1C
shows a side cross-sectional view of the conventional voltage coil of FIG.
1
A. In manufacturing a conventional voltage coil, one end of a wire
5
, such as copper, is captured in a terminal, then an operator inserts a terminal
10
into a first or start terminal mounting box
15
that is part of a bobbin
2
. The wire
5
is guided around the box
15
and through a slot
17
in an upper flange
20
and wrapped around the core
25
of the bobbin
2
a predetermined number of times or windings. It should be noted that the bobbin
2
also comprises a lower flange
22
, and the wire
5
is wound around the core
25
between the upper flange
20
and the lower flange
22
.
After the wire has been wound the predetermined number of windings, a piece of tape is applied to keep the wire from unwinding. The wire is again captured in a second or end terminal
30
and the end terminal
30
is then inserted into a second or end terminal mounting box
35
. In
FIG. 1A
, the wire
5
is shown as a dashed line toward its starting and ending points. The voltage coil is then sent for the subsequent steps of testing and encapsulation. The winding of the conventional voltage coil is labor intensive, and has a long manufacture cycle which leads to low productivity and high cost. Also, the encapsulation of the conventional voltage material uses a thermoset material which leads to a long cure time, poor yield, low productivity, and high cost.
U.S. Pat. No. 5,774,036, entitled “Bobbin-Mounted Solenoid Coil and Method of Making”, issued to Hrytzak et al., describes a solenoid coil in which a magnet wire (MW) is wrapped around a bobbin core (
24
) and terminals (
84
,
86
) are inserted into terminal sockets to connect to the magnet wire (MW). The solenoid coil is used in very low voltage applications, such as those in automotive vehicles (about 12 volts), and cannot be used in high voltage or electromagnet applications because the terminals are spaced too close together, thus resulting in the starting and ending points of the wire being close together. It should be noted that a solenoid is different from an electromagnet.
Although the art of voltage coils is well developed, there remain some problems inherent in this technology, particularly the ability for small coils having very fine magnet wire to handle high voltages. Therefore, a need exists for a voltage coil that overcomes the drawbacks of the prior art.
SUMMARY OF THE INVENTION
The present invention is directed to a coil for high voltage applications, comprising a bobbin comprising a core, an upper flange having a grooved step channel and a slot extending from the grooved step channel to the core, a lower flange, and a first terminal mounting box and a second terminal mounting box disposed on the upper flange; a wire wound around the core of the bobbin in a predetermined number of turns and having a first end disposed in the first terminal mounting box and a second end disposed in the second terminal mounting box; a first terminal positioned in the first terminal mounting box to secure the first end of the wire; and a second terminal positioned in the second terminal mounting box to secure the second end of the wire.
According to further aspects of the invention, the bobbin is made of a thermoplastic material, the wire comprises an insulated magnet wire, and the core is hollow, has a square cross-section, and is centrally disposed between the upper flange and the lower flange.
According to one aspect of the present invention, the first and second terminal mounting boxes are spaced apart sufficient to mechanically and electrically isolate the first and second ends of the wire. Preferably, the upper flange has a circumference and the first and second terminal mounting boxes are located at approximately one-quarter of the circumference.
In accordance with another aspect of the present invention, the first and second terminals comprise a plurality of serrations that contact the first and second ends of the wire, respectively. Moreover, the first terminal mounting box has a first lower slot and the first end of the wire extends from the first terminal through the first lower slot to the core, and the second terminal mounting box has a second lower slot and the second end of the wire extends from the core through the second slot to the second terminal.
In accordance with a further aspect of the present invention, the first end of the wire extends from the first terminal through the first lower slot, around and within the grooved step channel of the upper flange through the slot, to the core. Moreover, the grooved step channel comprises radial edges to minimize bends in the wire.
In a further embodiment within the scope of the present invention, a bobbin for use in a voltage coil section of an electromagnet is provided that comprises a core; a stepped upper flange having a grooved step channel and a slot extending from the grooved step channel to the core; a lower flange; and a first terminal mounting box and a second terminal mounting box disposed on the upper flange, wherein the core extends between the upper flange and the lower flange.
In accordance with a further aspect of the present invention, the bobbin further comprises a removable first tie off post disposed on the first terminal mounting box and a removable second tie off post disposed on the second terminal mounting box. The first and second tie off posts are used for securing a wire. Preferably, the first terminal mounting box has a first lower slot and a first upper slot, and the second terminal mounting box has a second lower slot and a second upper slot, and the slots are used for guiding the wire from the first and second tie off posts to the core.
Another embodiment within the scope of this invention includes a method for making a voltage coil comprising the steps of providing a bobbin that comprises a core, a stepped upper flange having a grooved step channel and a slot extending from the grooved step channel to the core, a lower flange, wherein the core extends between the upper flange and the lower flange, a first terminal mounting box and a second terminal mounting box disposed on the upper flange, the first terminal mounting box having a first lower slot and a first upper slot, and the second terminal mounting box having a second lower slot and a second upper slot, and a removable first tie off post disposed on the first terminal mounting box and a removable second tie off post disposed on the second terminal mounting box; providing a length of wire; securing a first end of the wire to the first tie off post; running the wire in tension from the first tie off post through the first upper slot and the first lower slot, along and within the grooved step channel of the upper flange through the slot, to the core; winding the wire a predetermined number of times around the core; running the wire in tension from the core through the second lower slot and the second upper slot to the second tie off post; securing a second end of the wire to the second tie off post; and mounting a first terminal in the first terminal mounting box and a second terminal in the second terminal mounting box
Broome Russell C.
Privette Ronald E.
Stephenson Roger D.
ABB Power T&D Company Inc.
Gellner Michael L.
Mai Anh
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
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