U.S. patent application number 13/720618 was filed with the patent office on 2013-05-02 for method for making inductor coil structure.
This patent application is currently assigned to VISHAY DALE ELECTRONICS, INC.. The applicant listed for this patent is VISHAY DALE ELECTRONICS, INC.. Invention is credited to Brett JELKIN, Timothy M. SHAFER.
Application Number | 20130106562 13/720618 |
Document ID | / |
Family ID | 38698763 |
Filed Date | 2013-05-02 |
United States Patent
Application |
20130106562 |
Kind Code |
A1 |
SHAFER; Timothy M. ; et
al. |
May 2, 2013 |
METHOD FOR MAKING INDUCTOR COIL STRUCTURE
Abstract
An electrical component is disclosed. The electrical component
includes a current conducting coil having inside and outside
surface and terminal ends that are configured for connection to an
electrical circuit and compressed iron particles that form a body
which completely contacts the inside and outside surfaces of the
coil for magnetically shielding the coil and leaving the terminal
ends exposed for connection to the electrical circuit.
Inventors: |
SHAFER; Timothy M.;
(Yankton, SD) ; JELKIN; Brett; (Windsor,
CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
VISHAY DALE ELECTRONICS, INC.; |
Columbus |
NE |
US |
|
|
Assignee: |
VISHAY DALE ELECTRONICS,
INC.
Columbus
NE
|
Family ID: |
38698763 |
Appl. No.: |
13/720618 |
Filed: |
December 19, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13109576 |
May 17, 2011 |
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13720618 |
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12535757 |
Aug 5, 2009 |
7986207 |
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13109576 |
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12013725 |
Jan 14, 2008 |
7921546 |
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12535757 |
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11782020 |
Jul 24, 2007 |
7345562 |
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12013725 |
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11609165 |
Dec 11, 2006 |
7263761 |
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11782020 |
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11409651 |
Apr 24, 2006 |
7221249 |
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11609165 |
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11038880 |
Jan 20, 2005 |
7034645 |
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11409651 |
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10244777 |
Sep 16, 2002 |
6946944 |
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11038880 |
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09546859 |
Apr 10, 2000 |
6449829 |
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10244777 |
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09271748 |
Mar 18, 1999 |
6198375 |
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09546859 |
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09547155 |
Apr 11, 2000 |
6460244 |
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10244777 |
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08963224 |
Nov 3, 1997 |
6204744 |
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09547155 |
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08503655 |
Jul 18, 1995 |
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08963224 |
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Current U.S.
Class: |
336/84C |
Current CPC
Class: |
Y10T 29/49073 20150115;
B29C 43/003 20130101; B29K 2995/0008 20130101; Y10T 29/49076
20150115; Y10T 29/49172 20150115; H01F 27/027 20130101; H01F 5/00
20130101; H01F 2017/048 20130101; H01F 27/292 20130101; Y10T
29/49146 20150115; Y10T 29/4902 20150115; Y10T 29/49158 20150115;
H01F 41/0246 20130101; B29C 43/18 20130101; H01F 37/00 20130101;
Y10T 29/49176 20150115; H01F 27/2847 20130101; B29K 2303/06
20130101; H01F 2027/2861 20130101 |
Class at
Publication: |
336/84.C |
International
Class: |
H01F 5/00 20060101
H01F005/00 |
Claims
1. An electrical component comprising: a current conducting coil
having inside and outside surface and terminal ends that are
configured for connection to an electrical circuit; and, compressed
iron particles that form a body which completely contacts the
inside and outside surfaces of the coil for magnetically shielding
the coil and leaving the terminal ends exposed for connection to
the electrical circuit.
2. An electrical component comprising: a current conducting coil
having inside and outside surface and terminal ends that are
configured for connection to an electrical circuit; and, compressed
iron particles that form a body which completely contacts the
inside and outside surfaces of the coil that magnetically shields
the coil and leaves the terminal ends exposed outside the body.
3. An electrical component comprising: a current conducting coil
having inside and outside surface and terminal ends that are
configured for connection to an electrical circuit; and, compressed
iron particles that form a body which completely contacts the
inside and outside surfaces of the coil, whereby the terminal ends
are exposed outside of the body and the coil is magnetically
shielded.
4. An electrical component comprising: a current conducting coil
having inside and outside surface and terminal ends that are
configured for connection to an electrical circuit; and, compressed
iron particles that form a body which completely contacts the
inside and outside surfaces of the coil and enhances induction and
efficiency of the coil.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 13/109,576, filed May 17, 2011, which is a continuation of U.S.
application Ser. No. 12/535,757 filed Aug. 5, 2009, now U.S. Pat.
No. 7,986,207; which is a divisional application of U.S.
application Ser. No. 12/013,725 filed Jan. 14, 2008, now U.S. Pat.
No. 7,921,546; which is a divisional application of U.S.
application Ser. No. 11/782,020 filed Jul. 24, 2007, now U.S. Pat.
No. 7,345,562; which is a divisional application of U.S.
application Ser. No. 11/609,165 filed Dec. 11, 2006, now U.S. Pat.
No. 7,263,761; which is a divisional application of U.S.
application Ser. No. 11/409,651 filed Apr. 24, 2006, now U.S. Pat.
No. 7,221,249; which is a divisional application of U.S.
application Ser. No. 11/038,880 filed Jan. 20, 2005, now U.S. Pat.
No. 7,034,645; which is a divisional application of U.S.
application Ser. No. 10/244,777, filed Sep. 16, 2002, now U.S. Pat.
No. 6,946,944; which is a continuation of U.S. application Ser. No.
09/546,859 filed Apr. 10, 2000, now U.S. Pat. No. 6,449,829; which
is a divisional of U.S. application Ser. No. 09/271,748, filed Mar.
18, 1999, now U.S. Pat. No. 6,198,375. U.S. application Ser. No.
10/244,777, filed Sep. 16, 2002, now U.S. Pat. No. 6,946,944, is
also a continuation of U.S. application Ser. No. 09/547,155, filed
Apr. 11, 2000, now U.S. Pat. No. 6,460,244; which is a divisional
of U.S. application Ser. No. 08/963,224, filed Nov. 3, 1997, now
U.S. Pat. No. 6,204,744; which is a continuation of U.S.
application Ser. No. 08/503,655 filed Jul. 18, 1995, now
abandoned.
FIELD OF INVENTION
[0002] The present invention relates to inductor coil structures
and methods for making same.
BACKGROUND
[0003] The coil structure of the present invention is preferably
for use in a high current low profile inductor commonly referred to
by the designation IHLP. However, the particular coil structure may
be used in other types of inductors.
[0004] Inductor coils have in the prior art been constructed from
various shapes of materials formed into various helical shapes.
However, there is a need for an improved inductor coil structure
which is simple to manufacture and which provides an efficient and
reliable inductance coil.
[0005] Most prior art inductive components are comprised of a
magnetic core having a C-shape, and E-shape, a toroidal shape, or
other shapes and configurations. Conductive wire coils are then
wound around the magnetic core components to create the inductor.
These types of prior art inductors require numerous separate parts,
including the core, the winding, and some sort of structure to hold
the parts together. Also, these inductive coils often have a shell
surrounding them. As a result there are many air spaces in the
inductor which affect its operation and which prevents the
maximization of space.
[0006] Therefore, a primary object of the present invention is the
provision of an improved inductor coil structure and method for
making same.
[0007] A further object of the present invention is the provision
of an inductor coil structure which can be used in a high current
low profile inductor having no air spaces in the inductor, and
which includes a magnetic material completely surrounding the
coil.
[0008] A further object of the present invention is the provision
of an inductor coil structure which includes a closed magnetic
system which has self-shielding capability.
[0009] A further object of the present invention is the provision
of an inductor coil structure which maximizes the utilization of
space needed for a given inductance performance so that the
inductor can be of a minimum size.
[0010] A further object of the present invention is the provision
of an improved inductor coil structure which is smaller, less
expensive to manufacture, and is capable of accepting more current
without saturation than previous inductor coil structures.
[0011] A further object of the present invention is the provision
of an inductor coil structure which lowers the series resistance of
the inductor.
[0012] A further object of the present invention is the provision
of a high current, low profile inductor which requires fewer turns
of wire in the coil to achieve the same inductance achieved with
larger prior art inductors, thus lowering the series resistance of
the inductor.
SUMMARY
[0013] An electrical component is disclosed. The electrical
component includes a current conducting coil having inside and
outside surface and terminal ends that are configured for
connection to an electrical circuit. According to an embodiment,
the electrical component may include compressed iron particles that
form a body which completely contacts the inside and outside
surfaces of the coil for magnetically shielding the coil and
leaving the terminal ends exposed for connection to the electrical
circuit. According to an embodiment, the electrical component may
include compressed iron particles that form a body which completely
contacts the inside and outside surfaces of the coil that
magnetically shields the coil and leaves the terminal ends exposed
outside the body. According to an embodiment, the electrical
component may include compressed iron particles that form a body
which completely contacts the inside and outside surfaces of the
coil, whereby the terminal ends are exposed outside of the body and
the coil is magnetically shielded. According to an embodiment, the
electrical component may include compressed iron particles that
form a body which completely contacts the inside and outside
surfaces of the coil and enhances induction and efficiency of the
coil.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a perspective view of the inductor constructed in
accordance with the present invention and mounted upon a circuit
board.
[0015] FIG. 2 is a pictorial view of the coil of the inductor
before the molding process.
[0016] FIG. 3 is a pictorial view of the inductor of the present
invention after the molding process is complete, but before the
leads have been formed.
[0017] FIG. 4 is an end elevational view taken along line 4-4 of
FIG. 2.
[0018] FIG. 5 is an elevational view taken along lines 5-5 of FIG.
4.
[0019] FIG. 6 is a perspective view of an elongated conductor blank
from which the inductor coil is formed.
[0020] FIG. 7 shows the blank of FIG. 6 after the formation of
slots extending inwardly from the opposite edges thereof.
[0021] FIG. 8 is a view similar to FIG. 7, showing the first
folding step in the formation of the inductor coil of the present
invention.
[0022] FIG. 9 is a side elevational view showing the same folding
step shown in FIG. 8.
[0023] FIG. 10 is a view similar to 8 and showing a second folding
step in the process for making the inductor coil of the present
invention.
[0024] FIG. 11 is an inverted pictorial view of the inductor after
it has been pressed, but before the leads have been formed.
[0025] FIG. 12 is a view similar to FIG. 11 showing the inductor
after partial forming of the leads.
[0026] FIG. 13 is a view similar to FIGS. 11 and 12 showing the
final forming of the leads.
[0027] FIG. 14 is a pictorial view of an inductor constructed in
accordance with the present invention and mounted upon a circuit
board.
[0028] FIG. 15 is a pictorial view of the coil of the inductor and
the lead frame which is attached to the coil before the molding
process.
[0029] FIG. 16 is a pictorial view of the inductor of the present
invention after the molding process is complete, but before the
lead frame is severed from the leads.
[0030] FIG. 17 is a flow diagram showing the method for
constructing the inductor of the present invention.
[0031] FIG. 18A is a sectional view of the lead frame and coil
mounted in a press.
[0032] FIG. 18B is a top plan view of FIG. 18A.
[0033] FIG. 18C is a view similar to FIG. 18A, but showing the
powder surrounding the lead frame and coil before pressure is
applied.
[0034] FIG. 18D is a view similar to 18A, but showing the pressure
being applied to the coil, lead frame, and powder.
[0035] FIG. 18E is a view similar to 18A, but showing the ejection
of the lead frame and the molded inductor from the mold.
[0036] FIG. 19 is a perspective view of a modified form of the
invention utilizing a coil of wire having a round cross
section.
[0037] FIG. 20 is an exploded perspective view of the lead frame
and coil of the device of FIG. 19 before assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0038] Referring to the drawings the numeral 10 generally
designates an inductor of the present invention which may be
mounted upon a circuit board 12. Inductor 10 includes an inductor
body 14 having a first lead 16 and a second lead 18 extending
therefrom and being folded over the opposite ends of body 14. Leads
16, 18 are soldered or otherwise electrically connected on the
circuit board 12.
[0039] Referring to FIG. 2, the inductor coil of the present
invention is generally designated by the numeral 20. Leads 16, 18
form the ends of coil 22. Between leads 16, 18 are a plurality of
L-shaped coil segments 26 each comprising a horizontal leg 28 and a
vertical leg 30. Vertical leg 30 terminates at a connecting segment
32 which is folded over at approximately 180.degree. so as to
create an accordion like configuration for inductor coil 20. The
L-shaped coil segments are connected together to form a helical
coil having an open coil center 34 extending along a longitudinal
coil axis 36.
[0040] FIGS. 6-10 show the process for making the coil 20.
Initially as shown in FIG. 6 a blank flat conductor plate 50 formed
of copper or other electrically conductive material includes: first
and second ends 52, 54; a pair of opposite flat surfaces 56; and a
pair of opposite side edges 58, 60.
[0041] FIG. 7 shows the first step in forming the coil 20. In this
step a plurality of slots 62, 64 are cut in the opposite edges 58,
60 respectively of the blank flat plate 50. Various cutting methods
may be used such as stamping or actual cutting by laser or other
cutting tools known in the art.
[0042] Upon completion of the cutting operation, the blank 50 is
transformed into an elongated sine shaped body formed from a
plurality of cross segments 66 extending transversely to the
longitudinal axis of plate 50 and a plurality of connecting
segments 67 extending axially with respect to the longitudinal axis
of plate 50. The segments 66, 67 form a continuous sine shaped
configuration as shown in FIG. 7.
[0043] FIG. 8 shows the next step in forming the coil 20. The end
52 is folded over at an angle of 180.degree. to form the
180.degree. angle bend 63 in the first connecting. segment 67. FIG.
10 shows a second bend 65 which is in the next connecting segment
67. Bends 63, 65 are in opposite directions, and are repeated until
an accordion like structure is provided similar to that shown in
FIG. 5.
[0044] In FIG. 5 the coil 20 includes opposite ends 16, 18 which
are formed from the opposite ends 52, 54 of blank 50. The cross
segments 66 of blank 50 form the first horizontal legs 28 of coil
20, and the connecting segments 67 of blank 50 form the second
vertical legs 30 and the connecting segments 32 of coil 20.
[0045] An example of a preferred material for coil 20 is a copper
flat plate made from OFHC copper 102, 99.95% pure.
[0046] The magnetic molding material of body 14 is comprised of a
powdered iron, a filler, a resin, and a lubricant. The. preferred
powdered material is manufactured by BASF Corporation, 100
Cherryhill Road, Parsippany, N.J. under the trade designation
Carbonyl Iron, Grade SQ. This SQ material is insulated with 0.875%
mass fraction with 75% H.sub.3PO.sub.4.
[0047] An epoxy resin is also added to the mixture, and the
preferred resin for this purpose is manufactured by Morton
International, Post Office Box 15240, Reading, Pa. under the trade
designation Corvel Black, Number 10-7086.
[0048] In addition a lubricant is added to the mixture. The
lubricant is a zinc stearate manufactured by Witco Corporation, Box
45296, Houston Tex. under the product designation Lubrazinc W.
[0049] Various combinations of the above ingredients may be mixed
together, but the preferred mixture is as follows:
[0050] 1,000 grams of the powdered iron.
[0051] 3.3% by weight of the resin.
[0052] 0.3% by weight of the lubricant.
[0053] The above materials (other than the lubricant) are mixed
together and then acetone is added to wet the material to a
mud-like consistency. The material is then permitted to dry and is
screened to a particle size of -50 mesh. The lubricant is then
added to complete the material 82. The material 82 is then ready
for pressure molding.
[0054] The next step in the process involves compressing the
material completely around the coil 20 so that it has a density
produced by exposure to pressure of from 15 to 25 tons per square
inch. This causes the powdered material 82 to be compressed and
molded tightly completely around the coil so as to form the
inductor body 14 shown in FIG. 1 and in FIGS. 11-13.
[0055] At this stage of the production the molded assembly is in
the form which is shown in FIG. 11. After baking, the leads 16, 18
are formed or bent as shown in FIGS. 12 and 13. The molded
assemblies are then baked at 325.degree. F. for one hour and
forty-five minutes to set the resin.
[0056] When compared to other inductive components the IHLP
inductor of the present invention has several unique attributes.
The conductive coil, lead frame, magnetic core material, and
protective enclosure are molded as a single integral low profile
unitized body that has termination leads suitable for surface
mounting. The construction allows for maximum utilization of
available space for magnetic performance and is magnetically
self-shielding.
[0057] The unique configuration of the coil 20 reduces its cost of
manufacture. Coil 20 may be used in various inductor configurations
other than IHLP inductors.
[0058] According to a second embodiment, inductor 10 is configured
as shown in FIG. 14 to be mounted on a circuit board 12. IHLP 10
includes an inductor body 14 having a first lead 16 and a second
lead 18 extending outwardly therefrom. The leads 16 and 18 are bent
and folded under the bottom of the inductor body 14 and are shown
soldered to a first pad and a second pad 21, 22 respectively.
[0059] Referring to FIG. 15 the inductor 10 is constructed by
forming a wire coil 24 from a flat wire having a rectangular cross
section. An example of a referred wire for coil 24 is an enameled
copper flat wire manufactured by H. P. Reid Company, Inc., 1
Commerce Boulevard, P.O. Box 352 440, Palm Coast, Fla. 32135, the
wire is made from OFHC Copper 102, 99.95% pure. A polymide enamel,
class 220, coats the wire for insulation. An adhesive, epoxy coat
bound "E" is coated over the insulation. The wire is formed into a
helical coil, and the epoxy adhesive is actuated by dropping
acetone on the coil. Activation of the epoxy can also be done by
heating the coil. Activation of the adhesive causes the coil to
remain in its helical configuration without loosening or
unwinding.
[0060] Coil 24 includes a plurality of turns 31 and also includes
an inner end 27 and an outer end 29.
[0061] A lead frame 33 formed of phosphor bronze, 510 alloy, which
is one half hardened, includes first lead 16 which has one end 35
welded to the inner end 27 of coil 24. Lead frame 33 also includes
a second lead 18 which has one end 38 welded to the outer end 29 of
coil 24. Leads 16 and 18 include free ends 37, 40 which are shown
to be attached to the lead frame 33 in FIG. 15. The welding of ends
35, 38 to the inner end 27 and the outer end 29 of coil 24 is
preferably accomplished by a resistance welding, but other forms of
soldering or welding may be used.
[0062] Referring to FIGS. 18A and 18B, a pressure molding machine
68 includes a platten 71 having a T-shaped lead frame holder 70 in
communication with a rectangular die 72. Platten 71 is slidably
mounted for vertical sliding movement on slide posts 74 and is
spring mounted on those posts 74 by means of springs 76. A base 78
includes a stationary punch 80 which projects upwardly into the
rectangular die 72 as shown in FIG. 18A.
[0063] The lead frame and coil assembly shown in FIG. 15 is placed
in the T-shaped lead frame holder 70 as shown in FIGS. 18A and 18B.
In this position the coil is spaced slightly above the upper end of
stationary punch 80.
[0064] Referring to FIG. 18C a powdered molding material 82 is
poured into the die 72 in such a manner as to completely surround
the coil 24. The leads 16, 18 extend outwardly from the powdered
material 82 where they are connected to the lead frame 33.
[0065] The magnetic molding material is comprised of a first
powdered iron, a second powdered iron, a filler, a resin, and a
lubricant. The first and second powdered irons have differing
electrical characteristics that allow the device to have a high
inductance yet low core losses so as to maximize its efficiency.
Examples of preferred powdered irons to use in this mixture are as
follows: a powdered iron manufactured by Hoeganaes Company, River
Road and Taylors Lane, Riverton, N.J., under the trade designation
Ancorsteel 1000C. This 1000 C material is insulated with 0.48% mass
fraction with 75% H.sub.3PO.sub.4. The second powdered material is
manufactured by BASF Corporation, 100 Cherryhill Road, Parsippany,
N.J. under the trade designation Carbonyl Iron, Grade SQ. This SQ
material is insulated with 0.875% mass fraction with 75%
H.sub.3PO.sub.4.
[0066] The powdered magnetic material also includes a filler, and
the preferred filler is manufactured by Cyprus Industrial Minerals
Company, Box 3299, Ingelwood, Calif. 80155 under the trade
designation Snowflake PE. This is a calcium carbonate powder.
[0067] A polyester resin is also added to the mixture, and the
preferred resin for this purpose is manufactured by Morton
International, Post Office Box 15240, Reading, Pa. under the trade
designation Corvel Flat Black, Number 21-7001.
[0068] In addition a lubricant is added to the mixture. The
lubricant is a zinc stearate manufactured by Witco Corporation, Box
45296, Huston, Tex. under the product designation Lubrazinc W.
[0069] Various combinations of the above ingredients may be mixed
together, but the preferred mixture is as follows: 1,000 grams of
the first powdered iron. 1,000 grams of the second powdered iron.
36 grams of the filler. 74 grams of the resin. 0.3% by weight of
the lubricant.
[0070] The above materials (other than the lubricant) are mixed
together and then acetone is added to wet the material to a
mud-like consistency. The material is then permitted to dry and is
screened to a particle size of -50 mesh. The lubricant is then
added to complete the material 82. The material 82 is then added to
the die 72 as shown in FIG. 18C.
[0071] The next step in the process involves the forcing of a
movable ram 87 downwardly onto the removable punch 84 so as to
force the punch 84 into the die 72. The force exerted by the
removable punch 84 should be approximately 15 tons per square inch
to 20 tons per square inch. This causes the powdered material 82 to
be compressed and molded tightly completely around the coil so as
to form the inductor body 14 shown in FIG. 14 and in FIG. 18E.
[0072] Referring to FIG. 18E an ejection ram 86 is lowered on to
platten 71 so as to force platten 71 downwardly against the bias of
springs 76. This causes the stationary ram 80 to eject the molded
assembly from the die 72. At this stage of the production the
molded assembly is in the form which is shown in FIG. 16. The
molded assemblies are then baked at 325.degree. F. for one hour and
forty-five minutes to set the polyester resin.
[0073] The next step in the manufacturing process is to severe the
lead frame 33 from the leads 16, 18 along the cut lines 42, 44. The
leads 16, 18 are then bent downwardly and inwardly so as to be
folded against the bottom surface of the inductor body 14.
[0074] The various steps for forming the inductor are shown in
block diagram in FIG. 17. Initially one of the wire ends 27, 29 is
welded to its corresponding end 35, 37 of leads 16, 18 as
represented by block 145. Next the coil is wound into a helix as
shown by block 146. Block 150 represents the step of welding the
other end 27, 29 to its corresponding lead 16, 18. The coil wire
includes an epoxy coat of bonding material described above. A
bonding step 149 is achieved by applying the acetone 148 or heat to
cause the bonding material to bind or adhere the various turns 31
of coil 24 together.
[0075] Next, at step 152 the powdered magnetic material is mixed
together adding ingredients 154, 156, 158, 160, and 162.
[0076] The pressure molding step 64 involves the application of
pressure as shown in FIGS. 18A through 18E. The parts are then
heated to cure the resin as shown in box 165.
[0077] Finally after the curing is complete the bending and cutting
step involves cutting off the lead frame 25 and folding the leads
16, 18 against the bottom surface of the inductor body 14.
[0078] Then compared to other inductive components the IHLP
inductor of the present invention has several unique attributes.
The conductive winding, lead frame, magnetic core material, and
protective enclosure are molded as a single integral low profile
unitized body that has termination leads suitable for surface
mounting. The construction allows for maximum utilization of
available space for magnetic performance and is magnetically self
shielding.
[0079] The unitary construction eliminates the need for two core
halves as was the case with prior art E cores or other core shapes,
and also eliminates the associated assembly labor.
[0080] The unique conductor winding of the present invention allows
for high current operation and also optimizes magnetic parameters
within the inductor's footprint.
[0081] The manufacturing processes of the embodiments provide a low
cost, high performance package without the dependence on expensive,
tight tolerance core materials and special winding techniques.
[0082] The magnetic core material has high resistivity (exceeding 3
mega ohms) that enables the inductor as it is manufactured to
perform without a conductive path between the surface mount leads.
The magnetic material also allows efficient operation up to 1 MHz.
The inductor package performance yields a low DC resistance to
inductance ratio of two milliohms per microHenry. A ratio of 5 or
below is considered very good.
[0083] Referring to FIGS. 19 and 20 a modified form of the
invention is designated by the numeral 88. Inductor 88 is formed
from a coil 90 of wire having round cross section. The coil 90
includes a first coil end 92 and a second coil end 94. A lead frame
96 includes a first lead 98 and a second lead 100 having first and
second lead ends 102, 104.
[0084] The method of assembly of device 90 is different from the
device 10 shown in FIGS. 14-18. With device 90, the coil is wound
first and is heat bonded during winding. Then the coil ends 92, 94
are welded to the lead ends 102, 104 respectively. The mixed
powdered material is then applied and the pressure molding process
is accomplished in the same fashion as described before. Finally
the leads 98, 100 are cut off and bent downwardly under the bottom
of the device 10.
[0085] The position of the leads 98, 100 can be varied without
detracting from the invention. Also, it is possible to put more
than one coil within a molded part. For example, it would be
possible to put two or more coils 24 within the molded body 10 or
two or more coils 90 within the molded body 89.
[0086] In the drawings and specification there has been set forth a
preferred embodiment of the invention, and although specific terms
are employed these are used in a generic and descriptive sense only
and not for purposes of limitation. Changes in the form and the
proportion of parts as well as in the substitution of equivalents
are contemplated as circumstances may suggest or render expedient
without departing from the spirit or scope of the invention as
further defined in the following claims.
* * * * *