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Патент USA US2407626

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Sept. 17, 1946;
A, U, WELCH, JR
n
`
2,407,626
MAGNETIC CORE
Filed Deo. 30, 1942
3 Sheets-Sheét l
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Inventor:
l
Alansor? LLM/eich J'f`,
QS
by jaw/f. Mw
Sept. 17, 1946.
_
A. u. wELçH, JR
MAGNETIC com.
Fi'led'nec. so, 1942
2,407,626
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:s sheets-sheet 2
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Y
inventori
Aœnsorw LLVVelcl’ï Jfìj
- Se'P-î- ~17, '1946.
A. u. WELCH, JR
`
MAGNETIC coRÈ
Filed 1m.l 30,71942
2,407,626
'
\
ssneets-sheet s
@a
/02
lmve?tor:
Al'anson LLWeIchJ'r:
His Attorney.
_
Patented Sept. 17, 1946
2,407,626
UNITED STATES PATENT OFFICE
2,407,626
MAGNETIC CORE
Alanson U. Welch, Jr., Pittsfield, Mass., assignor
to General Electric Company, a corporation of
New York
Application December 30, 1942, Serial No. 470,580
16 Claims.
(Cl. 175-356)
1
2
My invention relates to laminated magnetic
ful in the production of relatively small size
core structures for electrical induction apparatus
such as transformers and reactors.
transformers, which are called distribution trans
formers in the trade. Due to Various mechani
cal difficulties, however, it has been less eco
nomical to Wind much larger sizes of ribbon sheet
material so as to produce sufficiently large cores
for electric apparatus having a high kv.-a. ca
In the usual construction of magnetic cores,
the laminations are cut or punched from rela-
tively large stock sheets which are produced by
rolling from bars or billets of a suitable magnetic
material, such as various steel alloys, such as
silicon steel or a magnetic nickel iron steel. It
it known that the rolling process produces a
grain structure in sheets which may extend in the
direction in which the sheets have been rolled.
It is further known that the path of least mag
netic resistance of such material is generally
pacity.
Another way of providing cores of laminated
material in which the direction of flux path is
along the line of least magnetic reluctance in
the vicinity of the joints is to assemble the lami
nations, each corner of which has been cut on
the diagonal, so as to provide a mitered joint at
in the direction that the sheets have been rolled,
though in certain types of steels the most favor
each of the corners. It will be seen, however,
that when each of the joints at the various cor
able magnetic direction, in so far as low flux
losses are concerned, may be at sorne angle with
ners of the rectangular core are coincident with
the diagonal running from the inside corner to
respect to the direction of rolling. Thus, it will
the outside corner, all of the joints will be in sub
be seen that for optimum results for magnetic 20 stantial registry so that the possibility of gaps
cores it is desirable to cut the laminations from
being formed at the joints for increasing the
the sheets of magnetic material so that the core
magnetic reluctance is appreciable, even though
iiux path is parallel with the path of least mag
elaborate means are provided for clamping the
netic resistance, or parallel with the direction
magnetic laminations together.
of rolling even at the corners.
An improved arrangement for providing mi
25
One common form of magnetic core consists
tered joints at the various corners of the assem
of a stack of L shaped punchings, but it will
be apparent that such shapes cannot be punched
bled laminations and for preventing separation
at the joints is described and claimed in patent
as a single piece from a standard stock in such
application S. N. 376,304, Graniield, filed Janu
a manner that the most favorable magnetic direc 30 ary 28, 1941, and assigned to _the same assignee as
tion extends parallel with the flux path in both
this present invention. In that application there
parts of the punchings. This is due to the fact
is described a stacked laminated core formed of
that the grain extends in the same direction
laminations which have staggered mitered butt
throughout all parts of the stock while the two
joints with extensions and corresponding inden
parts of the L shaped punchings are at right 35 tations in the edges of the adjacent laminations,
angles to each other. Another common form of
so as to prevent an appreciable gap from being
a core consists of a rectangular core with adja
formed at the butt joint. The various layers
cent laminations being stacked at right angles
which are stacked to form the core are made
with respect to each other. While the most favor
up of similarly assembled laminations which are
able magnetic direction in this type of core may 40 oppositely arranged so as to stagger the joint
be made parallel with the direction of the ilux
between laminations between one layer and a
path throughout the central portion of the lami
contiguous layer. In this manner there will be
nations, the core iiux must cut crosswise of the
a minimum of magnetic iiux which will pass
most favorable direction at the ends of the lami
crosswise of the most favorable magnetic direc
nations in traversing from one core leg to the 45 tion and due to the projections and correspond
next. Due to this crosswise flow of flux at the
ing interñtting indentations which may extend
corners of the core, relatively high losses occur
in opposite directions for the adjacent joints of
at these points.
contiguous layers an overlapping will be provided
One way oi' overcoming the difliculties referred
at the joints so as to substantially preclude sep
to above is to provide a core structure by wind 50 aration of the laminations of the assembled
ing a ribbon of suitable magnetic steel so that
core.
al1 the nux will pass parallel to the direction
There is also described in an application S. N.
of rolling of the material or in the direction which
470,578 to Brand, filed concurrently herewith,
has the least magnetic reluctance. Such a type
and assigned to the same assignee as this pres
of wound core has been found to be very success 55 ent invention, a corner construction which pro
2,407,626
3
4
vides a minimum of magnetic reluctance at the
It having leg sheets II and I2 and yoke sheets
I3 and Iii, As has already been stated when
corners and which also provides overlap so as
to minimize separation of the stacks of the as
sembled core. In the construction of this copend
ing application mitered butt joints are provided
laminations are punched with edges which are
coincident with a diagonal running from an in
side corner to an outside corner of the assem
at the corners of each layer of laminations, the
bled lamination the joints will be in registry and
joints between laminations of one layer being
displaced or onset :from the adjacent joint or”
a contiguous layer. The offsetting is obtained
by cutting one edge of each of the laminations
on a diagonal so that the joints will be coin
thus there is a possibility of the adjacent lamina
tions of each layer pulling apart to form gaps at
the joints which will greatly increase the mag
netic reluctance of this circuit, It is therefore
desirable to stagger the joints and still provide a
cident with the diagonal running from the inside
mítered butt joint which type of joint produces
to the outside corner of the assembled lamina#
tions and cutting each of the other ends of the
laminations with a mitered butt joint which is
offset or displaced from a diagonal running from
the inside corner to the outside corner of the
assembled laminations. These latter joints are
obtained by notching the corner or providing
a minimum of magnetic reluctance at the joint or
corner as it provides a minimum of distance in
which the flux need pass crosswise of the most
between laminations oi one layer which is coin
the overlapping in which the flux must pass cross
wise oi the grain. I have found another ar
favorable magnetic direction.
One way of accomplishing this, as described
and claimed in the above~mentioned Brand ap
plication, is to provide butt joints which are co
a first portion which is parallel with a longitu 20 incident with the diagonal and butt joints in
which the major portion thereof is oiiset but still
dinal
of the assembled core and a second
parallel to the diagonal running from the inside
portion of a corner which is parallel with the
corner to the outside corner of the assembled
diagonal. The laminations are then stacked to
lamination. With such a construction an over
provide layers and the layers are oppositely ar
lapping will be provided when stacks of lamina
ranged so that the joints between laminations of
tions are oppositely arranged and a relatively
one layer will be offset from joints between lami
short distance will be provided at the corners at
nations of a contiguous layer. lI‘hus, a joint
cident with the diagonal will be adjacent to but
staggered from a joint of the adjacent or con
tiguous layer which is offset from the diagonal.
An object of my invention is therefore to pro
vide an improved corner construction between
laminations to form a core of the type described
in the aboveementioned Brand application,
Another object of my invention is to provide a
new and improved magnetic core stack of
Ipunched laminations which has a minimum of
30 rangement of providing overlap and producing a
minimum of magnetic path at the corners in
which the flux must pass crosswise of the grain
at the corners may be produced by so forming
the laminations that each of the mitered butt
joints at the corners will be offset from an adjaH
cent diagonal running from the inside corner to
the outside corner or" the assembled lamination.
With this construction each of the offsets may
be closer to the diagonal and still provide a suiii
electrical power loss throughout the magnetic
circuit.
40 cient overlap than with the construction where
all the overlap is provided by displacing the gap
A further object of Imy invention is to provide a
on one side only of the diagonal. Thus, in Fig. 1
I have illustrated a core construction including
simple in construction, economical to manufac
a layer Ill having laminations II, I2, I3 and I4,
ture, and eiiicient in operation.
Further objects and advantages of my inven 45 each of the laminations being provided With a
broken line joint the major portion thereof being
tion will become apparent from the following
parallel with the diagonal running from the in
description referring to the accompanying draw
side cor. er to the outside corner of the assembled
ings, and the features of novelty which charac
laminaticns. Thus, one edge of the lamination I I
terize my invention will be pointed out with par
ticularity in the claims annexed to and forming 50 has an edge surface I5 which is parallel with a
lateral axis of the assembled core or perpendicu
a part of this specification,
lar to the axis of the lamination, and a second
In the drawings Fig. 1 is an exploded perspec
new and improved core. construction which is
tive viewv of a laminated core comprising a plu
rality of layers of laminations formed according
edge portieri IB which is parallel with the adja
cent diagonal running Jfrom the inside corner I‘I
to an outside corner I8 of the assembled lamlna«
to an embodiment of my invention, Figs. 2 and
tions- In like manner the opposite end of the
3 illustrate curves which will be employed in the
lamination i i has an edge portion I9 parallel with
description of my invention; Fig. 4 illustrates a
the lateral axis of the assembled lamination and
method by which the laminations employed in
a second portion 20 which is onset but parallel
the core of Fig. 1 may be cut from a single strip
with
loss;
5 is an` exploded perspective view 60 to the adjacent diagonal running from the inside
corner to the outside corner of the assembled lam
f a three-legged core which is provided with an
mation. The adjacent end of the lamination I 3 is
embodiment of my invention; Fig, 6 illustrates a
so constructed as to snugly fit the broken line
method by which some of the laminations em
joints, the lamination i3 having an end portion
ployed in the core of Fig. 5 may be cut from a
single strip of magnetic material with a minimum 65 2l which is parallel with the lateral axis of the
assembled laminations or parallel tothe axis of
of waste; Fig. '7 is an exploded perspective view
the lamination IEB, and a second portion 22 which
illustrating- a modification of the three phase
is parallel with a diagonal running from the in
core of Fig. 5, and Fig. 8 illustrates a method by
side corner to the outside corner. Thus, the
which some of the laminations employed in the
construction of Fig. '7 may be cut from a strip of 70 portions of the joint which are parallel with the
diagonal are offset from the diagonal by an
magnetic material with a minimum of waste.
lin Fig. i of the drawings I have illustrated a
amount Iïi'oportional to the distance of the off
set portions I9 and I5 or notch 2|. In order to
magnetic core construction including a plurality
provide a corner for the assembled laminations
of assembled laminations to form layers of lami
which is offset from the portion 28 of the lami
nations. The assembled core includes a layer
5
52,407,626*
nation Il it will be seen that the edge portion
of the lamination I3 has a short portion 23 which
extends parallel with the longitudinal axis of
the core before the corner is formed. It will be
6
are overlapped. Thus, in Fig. 2 I have plotted on
the abscissa axis per cent loss and on the ordi
nate axis per cent flux density. Curve 50 rep
resents the loss in the corners of the conven
seen that the opposite end of the lamination I3
tional core made with rectangular sheets stacked
is similarly formed and therefore has a surface
with overlapping corners while curve 5I repre
Iportion 24 to provide a joint which is parallel
sents the characteristics of my improved corner
with the lateral axis of the assembled lamina
construction. In Fig. 3 I have illustrated the
tions, and a second portion 25 which is parallel
exciting current in which per cent exciting cur
and offset from the adjacent diagonal running l() rent is plotted as abscissa and per cent ñux den»
from the inside corner to the outside corner of
sity on the ordinate axis. Curve 52 represents
the assembled laminations. It will also be seen
the characteristics of an entire conventional core
that the lamination I2 is a duplicate or equiva
having rectangular overlapping corners while
lent to the lamination Il, While the lamination
curve 54 represents the characteristics of the en
I4 is a duplicate of the lamination I3.
tire core formed with my improved joint con
In order to provide a staggering of the joints
struction.
between the layer l0 and an adjacent layer 30
My improved corner construction not only pro
the laminations which form the layer 30 are
duces a core which is very efficient magnetically
` formed of laminations 3l, 32, 33, and 34. Since,
but it also produces a core which may be eni
in the construction as illustrated in Fig. l, the 20 ciently manufactured by punching out the vari
lamination 3l of layer 30 is placed at right angles
ous laminations from a single sheet of magnetic
to the lamination I3 of layer Il), the mitered butt
material having the proper flux orientation.
joint between the laminations 3| and 33 is placed
Thus, in Fig. 4 I have illustrated a strip of mag
on the side of a diagonal opposite to the joint
netic material 60 from which all the laminations
formed by the edges 20 and 22, by forming the
may be formed by punchings simultaneously with
ends of the lamination 3l similar to the ends of
two different dies and I have marked the punch
the lamination I3. Thus, the lamination 3l has
ings to show that the laminations fit together
an edge portion 35 which is parallel with the
so that they may be punched from the ribbon
longitudinal axis of the assembled lamination or
6i) with no waste.
parallel with the axis of the lamination 3|, and 30
In view of the above it will be seen that I have
a second portion 36 which is parallel with the
provided an assembled core formed of various
adjacent diagonal running from an inside cor
assembled layers which have a minimum of mag
ner 3'! to an outside corner 38 of the assembled
netic reluctance at the corners Furthermore,
laminations. In like manner the opposite end
the various laminations may be formed from strip
of the lamination 3l is formed with an edge por
material having a single width and may be
tion 33 which is parallel with the longitudinal
punched with only two different dies or with one
axis of the assembled laminations and a second
die if the steel is reversed for making alternate
portion 40 which is parallel but oiIset from the
cuts. Furthermore, the ends of all similar punch
diagonal running from an inside corner 4 I to
ings are similar and the laminations may be cut
an outside corner 42 of the assembled lamina 40 without waste.
tions. With this construction it will be noted
It is to be understood that my invention has
that the edge portions 20 and 22 will be on one
application for a core having any suitable number
side of the adjacent diagonal while the edge por
of punchings in each layer, and in Fig. 5 I have
tion 40 will be on the opposite side of a diagonal.
illustrated a core having three legs which has
This is obtained since the offset portions I9 and 45 particular application to a three phase electrical
2I at adjacent corners of the contiguous lami
apparatus. The illustrated construction includes
nations are parallel with the lateral axis of the
a layer 53 including three leg sheets and four yoke
assembled core, while the edge portion 39 is
Asheets which are so punched that the adjacent
parallel with the longitudinal axis of the core.
butt joints between laminations of contiguous
It will be seen that the lamination 33 has an 50 ilayers may be displaced on opposite sides of a
edge portion 43 which is parallel with the longi
diagonal running from an inside corner to an out
tudinal axis of the assembled laminations and
'side corner of the assembled laminations or some
a second portion 44 which is parallel with the
Ajoints are displaced on the leg side and some on
diagonal. Furthermore, the opposite end of the
the yoke side of the adjacent diagonal between
lamination 33 has a portion 45 which is parallel 55 inner and outer ends of the corner. Thus the
with the longitudinal axis of the assembled lam
layer 60 includes a leg sheet 6I, o-ne end having
inations and a second portion 43 which is parallel
an edge surface or notch 62 Iwhich is parallel with
with the diagonal. It will be apparent that the
a lateral axis of the assembled laminations and a
lamination 32 is an equivalent to the lamination
second edge portion 63 which is parallel but oiiset
3l while the lamination 34 is an equivalentl to 60 from an adjacent diagonal running from an in
the lamination 33.
side corner 64 to an outside corner 65 of the as
It will be seen in view of the above that when
sembled laminations. A cooperating yoke sheet
a layer IU is assmbled contiguously with a layer
66 has a straight or extending portion 5l which
30, the joints at corners of the contiguous lam
cooperates with the portion 62 of the leg sheet
inations will be symmetrically disposed on oppo 65 and a second portion 68 which cooperates with
site sides of the adjacent diagonal running from
the edge portion 63 of the leg sheet 6I. Similarly,
the inside corner to the outside corner. Thus an
a yoke sheet 69 is provided which is an equivalent
overlapping is provided with a minimum of fiux
to the yoke sheet 66 and includes a portion ‘lil
path being provided which is at an angle 0r
which cooperates with a notched portion 'Il of the
crosswise to the line of lowest magnetic resist 70 leg sheet 6l, both of which are parallel with the
ance.
lateral axis 0f the assembled laminations. The
remainder of the substantially mitered butt joint
I have illustrated in Fig. 2 a comparison be
is provided by a surface 'I2 of the lamination 619
tween the magnetic characteristics of my im
and a surface 'I3 of the leg sheet SI, both of
proved corner construction and the conventional i
construction having rectangular corners which 75 which are parallel and offset from a diagonal run-~
2,407,626;
ning between the corners of the assembled lam
inations. The oiïsetting of the joints at the ends
of the other cuter leg sheet 91 is provided by pro
viding the extensions in the leg sheet 91 instead
8
the only Iwaste is a small triangular piece which
must be removed from the ends of the yoke sheets
`Bti and 59 so that they will have the suitable `v'
shape to cooperate with the ends of the center
of in the yoke sheet, as is done on the opposite Ul leg and adjacent yoke sheets. The center leg 88
may be formed by cutting a triangularly shaped
side. Thus7 the leg sheet 91 is provided with an
piece from sheets having the shape of the leg
extension l!! or a portion parallel with the lon
sheets 6I and B1.
gitudinal axis of the assembled lamination, and a
In Fig. '1 I have illustrated a modification of
second portion which is parallel and offset from
a three legged core design which may be either
the adjacent diagonal. Cooperating with these
employed as a three phase core 0r since the cen
corner surfaces there is provided a yoke sheet 15
ter leg is about double the width of the two outer
having a portion 'l1 which is parallel with the
legs it may be advantageously used as a three
longitudinal axis of the assembled laminations
legged single phase core. The construction in
and a second portion "i3 which mates with the
cludes a layer of laminations IUE) having three
edge portion
of the leg sheet 91. Similarly a
leg sheets and four yoke sheets, the staggering
yoke sheet 19 is provided which has a similar con~
of joints being provided by an adjacent layer
ñguration as the yoke sheet 16 and includes an
IBI composed of laminations similar to those
edge portion tti which mates with an edge por
that make up layer |00 except being laterally.
tion 8| or the leg sheet 91. The yoke sheet 19
is also provided with an edge portion ¿i2 which 20 reversed. The layer IBG includes a leg sheet
|02 having an edge or notch |03 which is paral
cooperates with an edge portion 33 of the leg
lel with a lateral axis of the assembled lamina
sheet, these latter portions being parallel and oil'
tions and a second portion IM which is parallel
set from the adjacent diagonal. The opposite
to but offset :from a diagonal running between
end of the yoke sheet 19 is provided with an edge
the adjacent corners of the assembled lamina
mating surface portion t4 which is also parallel
tion. The adjacent yoke sheet |05 has an edge
with the longitudinal axis and a second portion
or extending portion |06 which cooperates with
85 which runs diagonally at a suitable angle such
the notch |53 and a second portion |01 which
as 45 degrees from the edge portion 84. In like
cooperates with the diagonal portion ||J4 of the
manner a similar end of the yoke sheet 16 is
provided with an edge portion 85 which is par 30 leg sheet |52. The opposite end of the leg sheet
ltd is similarly formed with an edge portion 0r
allel with the longitudinal axis of the assembled
notch |33 which is parallel with the lateral axis
lamination and a second portion 81 which runs
of the assembled laminations and a second por
diagonally at a suitable angle or ¿l5 degrees from
tion IUS which runs diagonally from the portion
the edge portion t5. Cooperating with the edges
of the yoke sheets there is provided edges of a
center leg sheet 88 and edges of the yoke sheets
5E and
rl‘hus the leg sheet S8 is provided
with an edge portion t9 which mates with the
|08 and parallel and offset from the diagonal
running between the corners of the
laminations. In like manner a yoke
is provided with a portion III which
portion Hi8 and a diagonal portion
assembled
sheet IID
mates the
I|2 which
portion Sill of the yoke sheet 19 and a second por
tion y9|) which mates with a part of the diagonally 40 cooperates with the portion |59. The other outer
leg sheet | i3 is provided with an extending p0r
extending edge 35. The remainder of the edge
tion II4 which is parallel with the longitudinal
85 cooperates with an edge 9| of the yoke sheet
axis of the assembled laminations and a second
59. Another angular edge portion il?. oi' the yoke
portion I I5 which runs diagonally and oiîset from
sheet G9 cooperates with a similar angularly ex
tending edge portion S3 of the leg sheet 8S. The 45 the diagonal running between the corners. Simi
larly a yoke sheet IIS is provided with an edge
angularly extending edge ‘93 is offset by providing
portion or notch I|1 which cooperates with the
another edge portion 94 of the leg 58 which is
edge portion |I4 and a second portion IIB which
parallel with the lateral axis of the assembled
cooperates with the portion |I5. The opposite
lamination. A similar edge portion
is pro
vided on the yoke sheet 59 which mates with the 50 end of the leg sheet I|3 is also provided with a
edge portion Bil. A similar joint is provided at
the other end oi the leg sheet
between the
joining surface including portions I|9 and |20
and an adjacent yoke sheet I2| has a notched
portion |22 which cooperates with the edge IIS
yoke sheets 55 and 15. It will therefore be seen
and a portion |23 which cooperates with the
that when stacking a layer of laminations 95
which is composed of laminations similar to that 55 edge portion |25. A center leg |24 is provided
having an extending portion |25 which cooper
forming a layer |59 but laterally reversed, the ad
ates with a similarly shaped notch portion |26
of the yoke sheet I2| which runs parallel with
the longitudinal axis of the assembled lamina
ning between corresponding inside and outside
corners of the assembled laminations.
60 tions and a diagonally extending portion |21
which cooperates with the portion |28 of the
In the construction illustrated. in Fig. 5 it will
yoke sheet I2I. The same end of the center
be seen that the joints at either endv or the leg
leg |24 is provided with a diagonal cut portion
sheet 6| are on the leg sheet side of the diagonal
|39 and a notch portion |3| which is parallel
while the joints on either end of the leg sheet 91
with the lateral axis of the assembled lamina
are on the yoke side of the diagonal of the assem
tions. Cooperating with these two surfaces is a
bled laminations. However, it is to be under
diagonally running portion |32 of the adjacent
stood that the joints of the laminations may all
yoke sheet | Ill and a portion |33 which runs par~
be staggered on one side or they may be staggered'
allel with the lateral axis of the assembled lami
on either of the sides of the diagonals between
the corners of the assembled laminations as is 70 nations. So that the yoke sheet IIU may be cut
jacent joints between contiguous laminations will
be on opposite sides of the adjacent diagonal run~
convenient.
from a ribbon sheet without a minimum waste a
In Fig. 6 I have illustrated how all the lamina
tions with the exception of the center leg sheet
88 may be punched from a single ribbon of steel
with a minimum or waste. It will beA seen that 75
upper end of the leg sheet |24 and the cooperate
ing ends of the yoke sheets |65 and IIïi are
corner may be cut oñî as is shown at |34.
similarly formed.
The
9.
2,407,626
Since all the laminations except the center leg
ysheet |24 are of similar width they may all be
10
of a major portion at azi angle of forty-five de
grees with the lengthwise dimension oi the
punching and a minor portion perpendicular to
punched from asimilar ribbon of steel and in
Fig. 8 I have illustrated how all the laminations
the lengthwise dimension of the punching, the
except the center leg §24 may be cut from a 5 two perpendicular minor portions at the opposite
single ribbon of steel with no waste and I have
ends of each punching being adjacent the same
illustrated by similar numerals how the various
side of the punching.
ends of the laminations ñt together with no
5. A laminated magnetic core having at least
waste.
iour punchings of magnetic strip material per
Although I have shown and described particu
layer, the two ends of each punching consisting
lar embodiments of my invention, I do not de
of a major bias cut portion and a minor portion
sire to be limited to the particular embodiments
out perpendicular to the lengthwise dimension
described, and I intend in the appended claims
of the punching, the two perpendicular minor
to cover all modifications which do not depart
portions at the opposite ends ol’ each punching
from the spirit and scope of my invention.
15 being adjacent the same side of the punching.
What I claim as new and desire to secure by
6. A punching for a mitered joint magnetic
Letters Patent of the United States is:
core, said punching having straight sides parallel
l. A magnetic core comprising a plurality of
with its lengthwise dimension and broken line
layers of assembled laminations formed length
ends, each broken line end comprising a minor
wise from strip material having the most favor 20 portion perpendicular to the lengthwise dimen
able magnetic direction lengthwise of the strip,
sion of the punching and a major portion mak
said layers including at least four assembled lami
ing an angle of forty-Ève degrees with the
nations with diagonal butt joints at adjacent
lengthwise dimension of the punching, said per
ends, said layers having at least two dissimilar
symmetrical laminations with each of said lami
nations having edge surfaces in six planes, edge
surfaces in four of said planes forming the edges
for said butt joints of said laminations.
2. A magnetic core comprising a plurality of
layers of assembled laminations formed length
wise from strip material having the most favor
able magnetic direction lengthwise of the strip,
adjacent laminations of each layer ,having sub
stantially mitered butt joints between ends so
pendicular minor portions extending for equal
distances from the same side of said punching,
said forty-five degree major portions being per
pendicular to each other.
'7. A punching for a mitered joint magnetic
core, said punching having straight sides par
allel with its lengthwise dimension and broken
line ends. each broken line end including a minor
portion perpendicular to the lengthwise dimen
sion of the punching, said perpendicular minor
portions extending for equal distances from the
that a minimum of ?lux passing from one lami
same side of said punching.
nation to another will pass crosswise of the most
8. A stacked lamination core having generally
favorable magnetic direction, said core structure
mitered butt joints in each layer which joints are
comprising three leg members and yoke members
staggered in adjacent layers, each layer compris
connecting the ends of said leg members form
ing a plurality of punchings having straight sides
ing a substantially rectangular core having two 4,1) parallel with their lengthwise dimension and
substantially rectangular windows, said mitered
having broken line ends, each broken line end
butt joints at the corners between said outer leg
comprising a minor portion perpendicular to the
and yoke members of said core structure being
lengthwise dimension of the punching, said per
oiîset from an adjacent diagonal running from
pendicular minor portions extending for equal
the inside corners to the outside corners of the 45 distances from the same side of said punching.
assembled laminations, said adjacent joints be
tween adjacent laminations of contiguous layers
being oiTset on opposite sides of said adjacent
9. A stacked rectangular magnetic core com
posed of two different kinds of leg punchings and
two different kinds of yoke punchings, said
diagonal so as to provide overlapping between
punchings all being o-f equal width with ends
adjacent laminations of contiguous layers at said 50 which are generally bias cut, odd-numbered
joints.
lamination layers of said core each comprising
3. A magnetic core comprising a plurality of
two leg punchings of the same kind and two
layers of assembled laminations formed length
yoke punchings of the said kind, even-numbered
wise from strip material having the most favor
layers each comprising two of the
able magnetic direction lengthwise of the strip, 55 lamination
other kind of leg punchings and two of the other
adjacent laminations of each layer having sub
kind of yoke punchings.
stantially mitered butt joints between ends so
l0. «A stacked rectangular magnetic core com
that a minimum of flux passing from one lami
posed of two diii‘erent kinds of leg punchings and
nation to another will pass crosswise of the most
two different kinds of yoke punchings, said
favorable magnetic direction, said core struc 60 punchings all being of equal width with ends
ture comprising three leg members
yoke mem
which are generally bias cut, odd-numbered lam
bers connecting the ends of said leg members
ination layers of said core each comprising two
forming a substantially rectangular core hav
leg punchings of the same kind and two yoke
ing two substantially rectangular windows, said
mitered butt joints at the corners between said 65 punchings of the same kind, even-numbered lam
ination layers each comprising two of the other
outer leg and yoke members of said core struc
kind of leg punchings and two of the other kind
ture being oiîset from an adjacent diagonal run
of yoke punchings, one kind of leg punching be
ning irom the inside corners to the outside cor
ing identical except for length with one kind of
ners of the assembled laminations, some of said
yoke punching and the other kind of leg punch
joints being oiîset on the leg side of said adja
70 ing being identical except for length with the
cent diagonal and some of said joints being off
other kind of yoke punching.
set on the yoke side of said diagonal.
1l. A stacked rectangular magnetic core com
4. A laminated magnetic core having at least
posed of two diiîerent kinds of leg punchings and
four punchings of magnetic strip material per
two diiïerent kinds of yoke punchings, said
layer, the two ends of each punching consisting 75 punchings all being of equal width with ends
2,407,626
11
12
which are interñtted to form generally mitered
which are generally bias out, odd-numbered lam
butt joints in each layer, all of said yoke punch
ination layers of said core each comprising two
ings and at least the two outside leg punchings
leg punchings of the same kind and two yoke
being of equal width, the center leg punching be
punchings of the same kind, eveii»numbered lam
ination layers each comprising two of the other Ui ing substantially twice as Wide as the othei`
punchings.
`
kind of leg punchings and two of the other kind
15. A single phase shell type laminated core
of yoke punchings, one kind of leg punching be
having a central winding leg and oppositely eX
ing identical except for length with one kind of
tending yoke portions which are substantially
yoke punching and the other kind of leg punch
narrower than the winding leg, said core being
ing being identical except for length with the
made of straight magnetic pieces in each lamina
other kind of yoke punching, the leg and yoke
tion layer, each piece having a most favorable
punchings in each layer being different in shape
magnetic direction coinciding with its length, the
as well as in length.
ends of said pieces being generally bias cut to
12. A laminated overlapping mitered joint
form mitered butt joints therebetween, said
magnetic core having at least four magnetic
mitered joints being offset from each other in
punchings per lamination layer, each of the mag
successive layers so as to form overlapping
netic punchings being symmetrical about an
mitered core joints.
imaginary bisector perpendicular to the length
16. A single phase shell type laminated core
of the punching.
having a central leg portion of twice the area oi
13. A three-legged magnetic core consisting of
its two oppositely extending yoke portions, said
stacked lamination layers, each layer comprising“
seven I type punchings of which three are leg
punchings and four are yoke punchings, all of
said punchings having generally bias cut ends
which are interiitted to form generally mitered
butt joints in each layer, all of said yoke punch
ings and at least the two outside leg punchings
being of equal Width.
14. A three-legged magnetic core consisting of
core being made of an equal number oi straight
magnetic pieces in each lamination layer, each
piece having a most favorable magnetic direction
coinciding with its length, the ends of said pieces
being generally bias cut to form mitered butt
joints therebetween, said mitered joints being oil
set from each other in successive layers so as to
form overlapping mitered core joints in which the
stacked lamination layers, each layer comprising 30 core flux will be substantially parallel with the
most favorable magnetic direction of the pieces.
seven I type punchings of which three are leg
punchings and four are yoke punchings, all of
ALANSON U. WELCH, JR.
said punchings having generally bias cut ends
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