U.S. patent number 3,713,066 [Application Number 05/111,849] was granted by the patent office on 1973-01-23 for inductors with strain relief leads and methods of making the same.
This patent grant is currently assigned to Kuhlman Electric Company. Invention is credited to John L. Fisher, Alan L. Wilks.
United States Patent |
3,713,066 |
Fisher , et al. |
January 23, 1973 |
INDUCTORS WITH STRAIN RELIEF LEADS AND METHODS OF MAKING THE
SAME
Abstract
This invention relates to methods and apparatus for connecting
coil leads to coil winding conductors and for protecting the
winding conductors from damage due to strain placed on the lead
conductors which are particularly well suited for use with
transformers and the like utilizing soft wires such as aluminum. In
an exemplary form of the invention, an insulation pad having an
opening for entry of the lead conductor is folded about a connector
which electrically connects the conductors. The ends of the folded
pad are captured within the coil so that the fold and connector are
positioned outside of the coil. Abutment of the connector on the
pad at the fold provides an external strain relief. The external
strain relief is supplemented by an internal strain relief provided
by capturing an end portion of the lead conductor within the
interior of the coil. The folded pad limits bending of the
connector assembly so as to enhance the durability of the
connection. Additional pads may be provided which surround the
folded pad to further reinforce the connector assembly and to
provide additional high voltage insulation. The lead connecting
methods and constructions of this invention may be used for start,
end or finish, and tap lead conductors.
Inventors: |
Fisher; John L. (Lexington,
KY), Wilks; Alan L. (Versailles, KY) |
Assignee: |
Kuhlman Electric Company (Troy,
MI)
|
Family
ID: |
22340774 |
Appl.
No.: |
05/111,849 |
Filed: |
February 2, 1971 |
Current U.S.
Class: |
336/192;
29/602.1 |
Current CPC
Class: |
H01F
41/10 (20130101); Y10T 29/4902 (20150115) |
Current International
Class: |
H01F
41/10 (20060101); H01f 015/10 () |
Field of
Search: |
;336/192 ;29/602 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Goldberg; E. A.
Claims
What is claimed is:
1. An apparatus comprising:
a coil body;
coil means wound on said body including at least one layer of a
winding conductor, at least one portion of said winding conductor
extending externally of said coil; and
a lead conductor connected to said external portion of said winding
conductor having one end extending and terminating internally of
said coil means and including a folded portion externally of said
coil so as to be captured by an interference fit between said
folded portion and the adjacent portion of said coil means to
protect said winding conductor from strains imposed on said lead
conductor.
2. An apparatus according to claim 1 further including connector
means providing said connection between said winding conductor and
said lead conductor.
3. An apparatus according to claim 1 wherein said lead conductor is
a start conductor for said coil means, said portion of said winding
conductor extending externally of said coil is proximate a
beginning of said winding conductor, and at least part of one layer
of said winding conductor overlies said one end of said lead
conductor to capture said one end.
4. An apparatus according to claim 1 wherein: said lead conductor
is a tap lead conductor, an intermediate portion of said winding
conductor extends externally of said coil and at least a part of
one layer of said winding conductor overlies said one end of said
lead conductor to capture said one end.
5. An apparatus according to claim 1 wherein: said lead conductor
is an end lead conductor, said portion of said winding conductor
extending externally of said coil is proximate an end of said
winding conductor, and wherein at least part of one layer of said
coil means which is not a layer of said winding conductor overlies
said one end of said lead conductor to capture said one end.
6. An apparatus comprising:
a coil body;
coil means wound on said body including at least one layer of a
winding conductor, at least one portion of said winding conductor
extending externally of said coil;
a lead conductor connected to said external portion of said winding
conductor having one end extending internally of said coil means so
as to be captured thereby in a manner to protect said winding
conductor from strains imposed on said lead conductor; and
insulation pad means extending externally of said coil on each side
of said connection of said lead conductor and said external portion
of said winding conductor for supporting said connection and
extending internally of said coil so as to be captured thereby.
7. An apparatus comprising:
a coil body;
coil means wound on said body including at least one layer of a
winding conductor, at least one portion of said winding conductor
extending externally of said coil;
a lead conductor connected to said external portion of said winding
conductor having one end extending internally of said coil means so
as to be captured thereby in a manner to protect said winding
conductor from strains imposed on said lead conductor;
connector means providing said connection between said winding
conductor and said lead conductor; and
insulation pad means extending externally of said coil on each side
of said connector for supporting said connector and extending
internally of said coil so as to be captured thereby. pg,14
8. An apparatus comprising:
a coil body;
coil means wound on said body including at least one layer of a
winding conductor, at least one portion of said winding conductor
extending externally of said coil;
a lead conductor connected to said external portion of said winding
conductor; and
insulating pad means extending internally of said coil to be
captured thereby and extending externally of said coil for
supporting said connection between said winding conductor and said
lead conductor and for restraining said connection in a manner to
protect said winding conductor from strains imposed on said lead
conductor.
9. An apparatus according to claim 8 further including connector
means at said connection providing said connection between said
winding conductor and said lead conductor.
10. An apparatus according to claim 8 wherein: said insulating pad
means is a member having a fold exterior of said coil with an
opening through said pad member at said fold, said lead conductor
extends through said opening to the interior of said folded pad,
said connection is relatively enlarged with respect to said lead
conductor for abutting the interior of said folded pad at said
opening so as to be captured thereby in a manner to protect said
winding conductor from strains imposed on said lead conductor.
11. An apparatus according to claim 10 further including connector
means providing said connection between said winding conductor and
said lead conductor which is relatively enlarged with respect to
said lead conductor and which abuts said pad member at said
opening.
12. An apparatus according to claim 10 further including additional
pad means on each side of said folded pad for providing additional
support for said connection between said winding conductor and said
lead conductor.
13. An apparatus according to claim 8 wherein: said insulating pad
means extends externally of said coil on each side of said
connection for supporting said connection.
14. An apparatus according to claim 8 wherein: said insulating pad
means including a portion adapted to be abutted by said connection
for providing said restraint of said connection.
15. An apparatus comprising:
a coil body;
coil means wound on said body including at least one layer of a
winding conductor, at least one portion of said winding conductor
extending externally of said coil;
a lead conductor connected to said external portion of said winding
conductor having one end extending internally of said coil means so
as to be captured thereby; and
insulating pad means extending internally of said coil to be
captured thereby and extending externally of said coil for
supporting said connection between said winding conductor and said
lead conductor and for restraining said connection;
said capture of said one end of said lead conductor and said
connection restraint being adapted to protect said winding
conductor from strains imposed on said lead conductor.
16. An apparatus according to claim 15 further including connector
means providing said connection between said winding conductor and
said lead conductor.
17. An apparatus according to claim 15 wherein insulated pad means
extends externally of said coil on each side of said connection for
supporting said connection.
18. An apparatus according to claim 15 wherein insulation pad means
including a portion adapted to be abutted by said connection for
providing said restraint and said connection.
19. An apparatus comprising:
a coil body;
coil means wound on said body including at least one layer of a
winding conductor, at least one portion of said winding conductor
extending externally of said coil; and
a lead conductor connected to said external portion of said winding
conductor having means associated therewith extending externally of
said coil means so as to be captured thereby and restraining said
connection in a manner to protect said winding conductor from
strains imparted on said lead conductor.
20. An apparatus according to claim 19 wherein said associated
means is a portion of said lead conductor.
21. An apparatus according to claim 19 wherein said associated
means includes a restraining member other than a portion of said
lead conductor.
22. A method for connecting a lead conductor to a winding conductor
for a coil comprising the steps of;
extending at least one portion of said winding conductor externally
of said coil;
connecting an external portion of said winding conductor to said
lead conductor;
positioning a portion of said lead conductor internally of said
coil so as to be captured thereby;
fixing an insulation pad means to said coil; and
restraining said connection with said insulation pad;
said capture of said lead conductor and said connection restrain
being accomplished in a manner to protect said winding conductor
from strains imposed on said lead conductor.
23. A method for connecting a lead conductor to a winding conductor
for a coil comprising the steps of:
extending at least one portion of said winding conductor externally
of said coil;
connecting an external portion of said winding conductor to said
lead conductor;
folding an end of said lead conductor; and
positioning said folded end of said lead conductor internally of
said coil so as to be captured thereby in a manner to protect said
winding conductor from strains imposed on said lead conductor.
24. A method for connecting a lead conductor to a winding conductor
for a coil comprising the steps of:
extending at least one portion of said winding conductor externally
of said coil;
connecting an external portion of said winding conductor to said
lead conductor; and
fixing an insulation pad means to said coil; and
restraining said connection with said insulation pad in a manner to
protect said winding conductor from strains imposed on said lead
conductor.
Description
SUMMARY OF THE INVENTION
In recent times, aluminum wire has been substituted for copper wire
in transformers and the like due to the shortage of copper. Since
aluminum is a relatively soft metal as compared to copper, it is
prone to failure when subjected to strains imposed through lead
conductors, i.e. conductors which extend externally of the coil for
various input and output functions.
The present invention provides methods and apparatus for securing
and electrically connecting the lead conductors to a winding
conductor of the coil which provides effective strain relief to
protect the winding conductor. In an exemplary construction
according to this invention, the tail end of a lead conductor is
captured by the coil to limit movement thereof so that any strain
placed on the lead conductor is not transmitted to the winding
conductor. The lead conductor may be connected to the winding
conductor by a relatively enlarged connection or connector which is
positioned outside of the coil body and which engages an insulation
pad folded about the connection having its folded portions captured
within the coil to provide an external strain relief. An opening in
the folded pad is provided at the fold through which the lead
conductor extends. It will be appreciated that the connection is
supported in its exterior location by the surrounding folded pad so
as to resist bending movement of the conductors at the connection.
Resistance to bending movement at the connection may be increased
by the provision of additional pads on each side of the folded pad.
Furthermore, it can be seen that placement of the connection
outside of the coil avoids a coil build which is uneven or of
excessive dimension.
In view of the above description it can be seen that effective
strain relief for the winding conductor is provided internally of
the coil by the captured lead conductor tail and externally of the
coil by the folded pad providing an engagement surface for the
connector. In addition to these advantageous strain relief
features, the methods and apparatus of this invention provide an
efficient coil construction, since the connection is placed outside
of the coil.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1-7 are illustrations of an exemplary method according to
this invention for connecting a start lead conductor to a winding
conductor;
FIGS. 8-12 are illustrations of an exemplary method according to
this invention for connecting a tap lead conductor to a winding
conductor; and
FIGS. 13-17 are illustrations of an exemplary method according to
this invention for connecting an end or finish lead conductor to a
winding conductor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIGS. 1-7, an exemplary method according to this invention is
illustrated for connecting a start lead conductor to a winding
conductor for a coil. As seen in FIG. 1, a coil assembly 10
consists of a core having a barrier 12 wound on the core to
partially encapsulate a plurality of insulating pads 14, e.g.
shellac coated paper boards. For example, the pads 14 may be wound
into the barrier beginning two turns from the initial layer of
barrier 12. As can be seen in the figure, the pads 14 extend
outwardly of the main assembly 10. The area in which the coil is to
be wound is indicated at 16 which is bounded on each side by a
barrier cuff 18. With reference now to FIG. 2, a folded shellac
coated paper board 20 is positioned over the winding portion 16 and
is secured with a tape strip 22 which may be a glass-filament tape
with a Mylar backing to provide acceptable strength. As can be seen
in FIG. 2, the fold of the paper board 20 is positioned beyond the
core structure 10 a distance less than the first pads 14. By way of
illustration, the first pads 14 may extend one inch from the core
structure 10 whereas the folded pad 20 may extend five-eighths of
an inch. The folded sheet 20 is provided with an opening 24 located
at the fold of the sheet 20 which is of predetermined size to
accommodate a lead conductor 26. As seen in FIG. 3, the lead
conductor 26, serving as a start lead, is inserted through the
opening 24 in the folded pad 20 and is provided with a crepe tubing
cover 28. Preferably, the left end of the lead conductor 26 is
folded at 30 to provide an interference fit after winding of the
coil to resist pull out of the lead 26 from the winding, and
additionally, to assure that the end of the lead conductor 26 will
not extend out of the opposite side of the coil to cause creepage
failure during operation. A coil conductor 32 is connected to the
lead conductor 26, for example, by an insulation piercing connector
34. After the connection, a tape strip 36 may be positioned on the
crepe tubing as shown and the lead conductor 26 and the connector
34 may be rotated approximately 360.degree. to wind the winding
conductor 32 around the crepe insulating tube 28, the conductor 26,
and the tape 36 to further secure the winding conductor 32 to the
lead conductor 26. After the rolling operation, the splayed ends of
the tape strip 36 are fastened to the assembly as shown in a
direction opposite the winding direction to absorb some of the
winding tension. An additional strip of tape 38 is used which
overlies the folded lefthand portion of the crepe tubing covered
conductor 26.
The connector 34 may be of the type illustrated in FIG. 4 which has
a generally tubular body 40 through which the lead conductor 26 and
the winding conductor 32 extend, and a plurality of insulation
piercing devices 42 therein. After the conductors 26 and 32 are
positioned within the housing 40, the connector 34 may be crimped
as illustrated in FIG. 5 to electrically connect the conductors 26
and 32. By way of example, the connectors 34 as illustrated in
FIGS. 4 and 5 may be of the variety obtainable from the Thomas and
Betts Company, Division of Thomas and Betts Corporation, Elizabeth,
N.J., and specifically, may be a connector listed by the
aforementioned company as catalog number 214420. The above
connector may be used in combination with a 14 Awg. aluminum magnet
wire and a 10 Awg. stranded lead conductor. It will be understood,
however, that other connectors may be used, and in fact, an
electrical connection may be made without the use of a
prefabricated connector. As will be apparent hereinafter, it is
desirable that the connection or connector assembly is of a size
which is substantially larger than the opening 24 for the lead
conductor 26 so that it cannot pass through the opening 24 under
expected strain conditions to provide an external strain relief.
For example, the opening 24 may be 0.094 for No. 14 and 18 Awg.
conductor and the above specified connector.
After the operations illustrated in FIG. 3 are performed, the pad
20 is folded over the tail of the lead conductor 26 as illustrated
in FIG. 6, and a crepe insulation tube 43 is positioned on the
external portion of the lead conductor 26 as illustrated in FIG. 6.
Additional pads 44 of shellac coated paper board are positioned on
top of the folded pad 20 and are secured by an appropriate tape
strip 46 as shown in FIG. 7. Thereafter, the operation of winding
the conductor 32 may be commenced.
After winding, the tail end of the lead conductor 26 and the ends
of the folded pad 20 are captured within the coil by the pressure
exerted by the winding of conductor 32. The aluminum magnet wire 32
is strain relieved internally by the wound-in tail of the lead
conductor 26. In this regard, it can be seen that the lead
conductor 26 passes directly through the connector 34 and is held
in position to absorb strains imposed on the lead conductor 26
without transmission of the strains to the winding conductor 32.
Additionally, the winding conductor is strain relieved externally
by the partial encapsulation of the connector 34 within the folded
pad 20. The connector 34 is allowed to abut the fold in the folded
pad 20 also to prevent any strains placed on the lead conductor 26
from being transmitted to the winding conductor 32. It can also be
seen that the connector 34 is placed outside of the coil so as to
avoid uneven build of the coil. As a still additional advantage,
the conductors at the connector 34 are protected from damage
through flexing since the connector 34 is intermediate relatively
rigid pads including the folded pad 20, the lower pads 14 and the
upper pads 44. It will be appreciated further that the coils are
ordinarily wound on cylindrical forms, and accordingly, the pads
will be bowed in accordance with the form to provide additional
strength and resistance to flexing at the connector 34.
Since like components are used in the following methods of FIGS.
8-12 and FIGS. 13-17, like numbers will be used to designate like
components. In FIGS. 8-12, a method is illustrated for connecting a
tap lead conductor to the winding conductor after the winding 40 is
partially completed. With reference now to FIG. 8, it can be seen
that two base pads 14 are laid over the partially completed coil
assembly 10 with the pads 14 projecting from the coil assembly 10.
Thereafter, a folded pad 20 having an opening 24 at the fold is
positioned over the pads 14 with the fold projecting from the coil
assembly 10 and is secured in position by a tape strip 22. Next,
the winding conductor 32 is provided with a 90.degree. bend as
shown and is extended to the right to have a portion positioned
externally of the coil opening 10 adjacent the opening 24 in the
folded pad 20. It may be terminated at that point as shown. The
winding conductor 32 returned to the left and provided with another
90.degree. bend so as to be aligned with the last winding of the
coil so that the winding operation may be continued after the lead
conductor is connected and secured. A tap lead conductor 52 is
inserted through the opening 24 in the folded pad 20 and is
fastened to the two ends of the winding conductor 32 by a connector
34. As can be seen in FIG. 10, the tap lead conductor 52 has a tail
extending substantially along the entire width of the coil assembly
10 which has been provided with an insulating crepe tube 28 and has
been folded at its end portion as previously described. The tail of
the tap conductor 52 may be secured by a tape 38 and the extensions
of the winding conductors 32 may be secured by a tape 53 which has
splayed ends affixed to the folded pad 20 generally in a direction
opposite the direction in which strain due to continued winding is
imposed. After the above steps, the folded pad 20 is folded over
the connector 34 and the tail of the tap lead conductor 52 as
illustrated in FIG. 11. A crepe tube 43 is inserted onto the tap
lead conductor 52 and additional pads 44 are placed over the folded
pad 20, and are secured by a tape 46. After this operation, the
winding operation is continued so as to encapsulate the above
structure to provide a strain relief for the winding conductor 32
by virtue of the captured tail of the tap conductor 52 and the
capture of the connector 34 by the folded pad 20.
In FIGS. 13-17, a method along the lines of the above methods is
disclosed for connecting the last turn of the winding 50 to a lead
conductor. According to this method a plurality of pads 14 and an
overlying folded pad are secured by a pair of tape strips 22. The
end of the winding conductor 32 is extended over the folded pad 20
and a right angle is formed at its end so that its end is adjacent
the opening 24 in the folded pad 20 as illustrated in FIG. 14. The
final lead conductor 54 is inserted through the opening 24 so that
a substantial portion of its tail extends over the coil assembly.
The tail is provided with a crepe tube 28 and folded as shown in
FIG. 15. The end of the winding conductor 32 and the lead conductor
54 are connected by a connector 34 in the manner previously
described. Thereafter, a tape 56 is placed over the winding
conductor 32 and the lead conductor 54 and the lead conductor 54
and the connector 34 are rotated approximately 360.degree. to wrap
the winding conductor 34 about the crepe covered lead conductor 54
and the tape 56. The splayed ends of the tape 56 are then secured
to the assembly 10 generally in a direction opposite the direction
of the winding conductor 32 so as to oppose the winding strain
thereon. A tape 38 is laid over the fold tail portion of the end
lead conductor 54 to secure the tail of the lead conductor 54.
Finally, the pad 20 is folded as illustrated in FIG. 16 and is
secured in the folded position by a tape 46. A crepe insulating
tube 43 is inserted over the conductor 54 as shown in FIG. 16.
Thereafter, an outer barrier 58 is wrapped one turn about the
assembly and several pads of shellac coated paper board 60 are
placed on the barrier 58 as shown in FIG. 17, after which the
winding of the barrier 58 is completed.
The various pads 14, 44 and 60 are determined in number and size in
accordance with established engineering considerations. For
example, the thickness and width of pads are established in part to
prevent the winding from cutting through the pads to prevent
electrical puncture, and to allow some misalignment of the tail of
the lead conductor without shorting. The length is normally
established in accordance with coil width to provide even coil
build so that the paper and winding conductors will track evenly
while being wound. More pad layers are used under the connection 34
for the start lead conductor than over the connection 34 for since
the start lead is a high voltage lead which is immediately above
the low/high barrier, and consequently, the puncture and creepage
voltage stress is quite severe at that locality, while the voltage
stress from the start lead conductor to the next upper layer of the
primary winding is considerably less.
In view of the above description of exemplary methods according to
this invention, it can now be seen that the winding conductor is
strain relieved both internally of the coil and externally of the
coil by a combination of a captured tail of the lead conductor and
a folded pad restraining the connector. Although these are most
effectively used in combination, each of these features may be used
individually. In addition to the excellent capture advantages of
this invention, excessive coil build up at connection locations is
avoided since the connectors are placed outside of the coil.
While it will be apparent that the teachings herein are well
calculated to each one skilled in the art, the method of making
preferred embodiments of this invention, it will be appreciated
that the invention is susceptible to modification, variation and
change without departing from the proper scope of meaning of the
subjoined claims.
* * * * *