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L. E. LAWRENCE
1,927,346
ELECTROMAGNETIC DEVICE
Filed June 50, 1932
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Sept. 19, 1933.
L. E, LAWRENCE
ELECTROMAGNETIC DEVICE
Filed June so, 1932 '
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L. E. LAWRENCE
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Filed June 30, 1932
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Sept. 19, 1933.
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Patented Sept. 19, 1933
' UNITED STATES
1,927,346
PATENT OFFICE
1,927,346 '
ELECTROMAGNETIC DEVICE
Leland E. Lawrence, La Grange Park, Ill., as
sig'nor to Western Electric Company, Incorpo
rated, New York, N. Y., a. corporation of New
York
Application June 30, 1932. Serial No. 620,095
32 Claims. (Cl. 17 5-340)
This invention relates to electromagnetic de
Fig. 18 is a fragmentary plan view of another
vices and more particularly to devices responsive
to electric currents or voltages, such as electrical modi?cation of the device;
19 is a sectional view taken‘ on line 19-19
measuring instruments, and is a continuation in of Fig.
Fig. 18;
Fig. 20 is a sectional view taken on line 20-20
545,659, ?led June 20, 1931.
65
An object of the invention is to provide a of- Fig. 19; and
Fig. 21 is a fragmentary section taken on line
sensitive and accurate device responsive to elec
21—-21 of Fig. 19.
tric currents or voltages.
5 part of my copending application, Serial No.
10
Referringvnow more in detail to the drawings,
In accordance with one embodiment of the in
vention, a device having a movable coil is pro Figs. 1 to 5 illustrate an embodiment of the in
vided having a source of magnetomotive force vention in a direct current measuring device. 70
within the coil and a magnetic circuit outside of
22 provided with a window 23
the coil which may. serve as a shield against stray
15 magnetic ?elds from outside sources. The pro
through which a calibrated scale 24 and a pointer
vision of the source of magnetomotive force 25 of the device may be seen. The device is
Cl
within the ' movable coil insures a minimum mounted upon a bracket 26 which is secured to
base
of
the
casing
21
and
is
amount of leakage ?ux and thus increases the
laterally extending arm 27 on
e?’ectiveness of the device.
20
A complete understanding of the invention may carrying the scale is supported.
The device is provided with an internal cylin
be had by reference to the following description
taken in conjunction with the accompanying drical core 31, which is a permanent magnet and 80
drawings, in which
is preferably made of cobalt or other steel having
Fig. 1 is a plan view of a device embodying
the invention;
Fig. 2 is a sectional view taken on line 2—2
of Fig. 1;
_
Fig. 3 is a sectional view taken on line 3——3
a high remanence and high coercive force and
acts as a source of magnetic potential for the
device. The ends of the cylindrical core are
reduced in diameter, forming a ledge 32 ex
85
tending circumferentialiy around the cylinder at
of Fig. 2;
either end. The magnet 31 has two pole pieces
33 secured thereto which are arcuate, cylindrical
sections and each pole piece extends over less
Fig. 5 is an enlarged fragmentary sectional than half the circumference of the cylindrical
View of the yoke, bridge, and the support for magnet as shown in Fig. 4. These pole pieces are
made of magnetic material, such as iron soft
central core shown in full in Fig. 2;
35
Fig. 6 is a plan view of a modi?ed form of the steel, or other suitable material, and serve to dis
tribute the magnetic ?ux uniformly from the per
invention;
95
Fig. 'lis a sectional View taken on line 7--7 manent magnet cylinder 31 over a substantial
area of the periphery of the cylinder. The pole
of Fig. 6;
.
Fig. 8 is a sectional view taken on line 8-8 pieces 33 are provided with a circumferential cut—
4.0 of Fig. 6;
out portion at their ends providing ledges 34 in
which
rings 35 of non-magnetic material, such
Fig. 9 is a sectional'view taken on line 9—9
of Fig. 7;
as brass, are adapted to ?t, thus holding the pole 109
Fig. 10 is a plan view of a modi?ed form of pieces securely to the cylindrical permanent
30
Fig. 4 is a sectional View taken on line 4-4.
of Fig. 2;
the invention;
5
magnet 31.
‘
Surrounding the permanent magnet and the
Fig. 11 is a side elevation of the device shown
pole pieces is a cylindrical yoke 36 of magnetic
in Fig. 10 with the outer shell or yoke removed;
material
which completes the magnetic circuit of 105
Fig. 12 is a sectional view taken on line 12—-12
the permanent magnet in two parallel branches
of Fig. 10;
to reduce the reluctance to the magnetic flux
Fig. 13 is a diagrammatic view showing the from
the permanent magnet located centrally of
circuit arrangement in this embodiment of the the yoke. The yoke 36 may be made of any suit
invention;
Fig. 14 is a vertical section of another embodi
able magnetic material, such as soft iron or a 110
nickel-iron alloy known as permalloy. The yoke
ment of the invention;
36 has an axially extending flange 37 at either
Big. 15 is a sectional view taken on line 15-15 end and a bridge 38 of non-magnetic material,
of Fig. 14;
such as brass, is adapted to ?t within each ?ange,
Fig. 15 is a sectional view taken on line 15-45 as shown in Fig. 2. It has been found that it is
on line 16—16 of Fig. 14;
dif?cult to provide screw apertures with sur?
Fig. 17 is a diagrammatic View showing the cient accuracy to obtain a proper centering of the
60 circuit arrangement of this embodiment;
bridge. By ?tting the bridge within the ?ange
37, the center of the bridge is accurately posi
n
2
1,927,846
tioned along one diameter of the cylinder and in
order to center the bridge with respect to a nor
mal diameter, a pair of arcuate ring sections 39
are placed within the ?anges 3'7 with their ends
abutting against the bridges 38, or the ring sec
tions may be integral with the bridges and placed
as units within the ?anges. Each of the bridges
38 has a pair of inwardly extending projections 41
which pass through slots 42 in rings 35, between
10 the side faces of pole pieces 33, and into engage
cal magnet 31. This magnet is magnetized in
such a direction that one of its poles will lie on
an axial line midway of the arc of one of the
pole pieces and the other pole with he on an axial
line midway of the arc of the other pole piece.
It has been found that in a device such as de
scribed with the fleld core surrounding the mova
ble coil, the field core acts as a shield against stray
external magnetic fields so that the device is un
affected by such fields.
A current to be measured is led to the movable
ment with the ledges 32 of cylinder 31. Thus coil 44 through leads 58 attached to adjusting
when the bridges are in position the core and levers 52, causing the ?ux produced by the coil to
pole pieces will be accurately and positively po coact with the ?ux in the air gap produced by the
sitioned relative to each other and centered with permanent magnet 31. The de?ection of the coil
15 in the cylindrical yoke.
Each of the bridges is
provided with a threaded aperture for receiving a
screw 43 which carries a jewel bearing at its inner
end.
Surrounding the pole pieces 33 and ‘movable
20 within the air gap between the pole pieces and
will be proportional to the current therein and
may be read on the scale by the position of pointer
25 carried by the coil.
Figs. 6 to 9 illustrate an embodiment of the in
vention in a measuring instrument for alternating 05
electrical currents. The device is mounted in a
the yoke is a movable coil 44 wound upon a sub casing 61 by means of a bracket 62 which is
stantially rectangular form 45 of aluminum or secured to the base of the casing and has a lateral
. other suitable material. This form is preferably ly extending arm 63 for supporting a calibrated
channel-shaped and has a number of turns of scale 64. The device is provided with an inner 100
25 wire wound between the ?anges of the channel. laminated core 65 of soft iron or a nickel-iron
A pair of plates 46 is adhesively secured to the alloy known as permalloy which has slots 66 in
coil and the plates have axially extending studs which a coil adapted to be energized by an alter-_
4'7 which are threaded for a portion of their nating current is wound. The outer faces 68 of
length and have reduced ends which act as pivots the core are arranged eccentrically about the 106
30 for engagement with the jewel bearings in the center of the core to provide a tapering rir gap
screws 43. The upper stud 4'7 carries the pointer 69 with a laminated yoke '71 to permit the use of
25 and each of the studs carries a washer held a scale having equal divisions. The laminations
on the stud by a nut 48 and provided with a pro of the central core 65 are held together by means
jection 50. One end of the movable coil 44 is
of rivets '72. The laminations of the yoke '71 are 110
35 electrically connected to one of the projections 50 made of similar material as the core and are
and the other end of the coil is electrically con
between a plate '73 of bakelite or other
nected to the other projection 50. Spiral springs clamped
suitable non-magnetic material and a cup-shaped
51 have their inner ends connected to the projec ring '74 of similar material. A movable coil '75
tions 50 while their outer ends are connected to is rotatably mounted in the air gap 69 and has a
40 levers 52. These levers are mounted upon collars stud '76 attached to one side thereof, and a shaft
40 surrounding screws 43 and secured to the
'77 attached to the other side thereof, which ex
bridges 38. The collars 40 are provided with in tends
through an opening in the cup-shaped ring
sulating washers 53 having insulating collars sur
'74. Underneath the cup-shaped ring '74 is a sec
rounding collars 40. The levers 52 fit over the ond cup-shaped ring '78 which, together with the 120
45 insulating collars and a second washer 54 is base of the cup-shaped ring '74, forms a pocket '79
placed over each of the levers and engages the for a damping vane attached to the shaft '77.
collar of washer 53. The washers 53 and 54 The cup-shaped ring '78 has a pair of inwardly
are forced into frictional engagement with the extending partitions 82 which separate the pocket
levers 52 by locknuts 55; thus the nuts 55 serve '79 into two parts, one for each half of the vane, 125
50 a double function of forming locknuts for the in accordance with a practice well known in the
screws 43 and frictionally positioning the levers art, to produce a damping action on the move
52. The purpose of the levers 52 is to adjust the ment of the coil. The ring '73 has two upwardly
pointer 25 to zero position when no current is extending projections 83 which cooperate with
passing through the device and also to serve as the cross-piece 84 to form a bridge for carrying a
55 terminals for the coil. The lower lever 52 is pref
screw 85 provided with a jewel bearing for one
erably used for adjusting the device prior to its pivot point of coil '75 and the cup-shaped ring
assembly in the casing 21, since this lever is not '78 is provided with two downwardly extending
readily accessible when the device is mounted in projections 86, cooperating with a cross-piece 8'7
135
the casing. The upper lever 52 may be adjusted
to form a support for screw 38, which carries a
60 to accurately set the device on zero to compen
jewel bearing for the other pivot of the coil at
sate for small deviations occurring after the as tached to the end of shaft '77. Electrical connec
sembly of the device in the casing. Conductors tion is made to the movable coil through adjust
are secured to the levers 52 and the current passes ing levers 89 in a manner similar to that described
140
from one lever 52 through coil spring 51, projec
in connection with the embodiment of the inven
65 tion 50, stud 4'7, through the coil, and out of the tion disclosed in Figs. 1 to 5. The stationary coil
other side of the coil in the same manner.
surrounding core 65 is provided with leads 91 for
In order to facilitate assembly of the device,
to an electrical circuit. The movable
the permanent magnet is preferably not mag connection
coil '75 and the stationary coil 6'7 are preferably 145
netized until after assembly of the device because connected in series to maintain a ?xed phase rela
70 the magnetization of the permanent magnets tionship between the currents in these coils.
tends to cause the magnet to be attracted and This device is extremely sensitive and due to the
adhere to other parts, such as the yoke. After fact that the field core surrounds the movable coil,
the device is assembled, it is placed in a strong as well as the ?xed coil, these coils are shielded
150
magnetic ?eld which will saturate the yoke and against stray fields from external sources.
is apply high magnetic potential across the cylindri
1,927,346
3
In Figs. 10 to 13 an embodiment of the inven
tion in a direct current relay is shown. The
device is mounted upon a base 101 of bakelite
washers 147 and 148 which are insulated from
each other and held upon the stud 121 by a
or other suitable insulating material. This base nut 151. The washers 147 and 148 are provided
has upwardly extending posts 102 imbedded with suitable projections to which ?exible con
ductors 152 and 153 are attached. The ?exible 80
therein and an outer shell or yoke 103 is pro
vided with suitable apertures for receiving these conductors are secured to posts 154 and 155 em
posts to securely hold the base and yoke together. bedded in the base 101.
The circuit from post 154 leads through a
The base 101 is provided with a pair of projections
10 104 along the sides thereof for positioning a plu
resistance coil to a terminal post157 and the
rality of bar magnets 105 which form a composite circuit from post 155 leads through a resistance
magnet for the device. The bar magnets may be coil to a terminal post 158. These resistance
made of cobalt steel or other suitable permanent coils form a composite coil 156 which is non
magnet material having a high remanence and inductively wound. that is, the conductors from
15 high coercive force.
posts 154 and 155 are wound side by side in
The bar magnets are held in place on the base bi?lar arrangement to eliminate the eifect of in
ductance during variations in the current sup
by a pair of clamps 106 of insulating material. plied
to coil 118.
These clamps are provided with transverse
Relays of this type have many uses, among
grooves for receiving terminal supports 107 se
20
cured to the base and to the clamps by bolts 108. which may be mentioned the regulation of cur
rents or voltages. When the current in a circuit 95
The terminal supports 107 are electrically con
nected to terminal posts 109 through the bolts 108 to which the device is connected reaches one
and connecting plates 111. Each of the terminal of the points at which a signal is given, steps
supports 107 has a terminal screw 112, provided may be taken to correct the value 01' the current
and return it to the desired value.
with a knurled head, mounted therein for a pur
Referring now to Figs. 14 to 17 of the draw 100
pose to be described hereinafter.
The bar magnets 105 are provided with arcuate ings, illustrating another embodiment of the in
ends forming a composite are about the center vention in a direct current relay, a base 160 is
provided of insulating material upon which is
mounted frame 161, formed with depressed por-=
to provide an air gap‘ for a movable coil 118. tions for receiving bar members which form a 105
This coil consists of a plurality of convolutions composite magnet 162, separated by an upwardly
of wire wound upon a channel-shaped frame projecting supporting member 163 integral with
119 of aluminum or other suitable material. the frame 161. The bar members, which com
Adhesively secured to the sides of the coil is pose the magnet 162, are positioned with like
a pair of studs 121 and 122 which carry pivot poles adjacent each other and are held against 110
points adapted to be journaled in jewel bear displacement by a suitable clamp 164. A yoke
ings carried by screws 123 and 124. The base 165 is mounted upon the frame 161 and has cut
30 of curvature of the ?eld core 103 at a shorter
radius than the inner periphery of the field core
40
101 is provided with a pair of apertures 113
away portions 166 and 167 therein to provide a
for receiving standards for hearing supports 114 relatively short air gap at the ends and for
and 115. The bearing support 114 is electrically short distances along the sides from the ends 115
connected to a terminal post 120 through a screw
116 and a plate 117, as shown in Fig. 12. The
45 screw 123 is mounted on standard 115 and is
secured in position by a locknut 125. The screw
124 is threaded into a collar 126, which is clamped
into the standard 114. This standard has a
slot 127 which permits the screw 128 to be turned
50 down to cause the standard to ?rmly grip the
collar. The end of the screw is provided'with
a locknut 129 to prevent rotation of the screw.
Integral with the collar 126 is a disc 131 having
a laterally extending projection 132 formed
therein. This projection is attached to the outer
end of a spiral spring 133, the inner end of
which is attached to a projection 134 of a washer
135. The washer, together with a pointer or
contact arm 136, is secured to the stud 122 of
the movable coil by a nut 137. t It will be seen,
therefore, that the contact arm 136 is electri
120
volutions of wire. Pivot bases 175 and 176 ?xedly
mounted upon the coil 168 but insulated from it
contain pivots 177 which have their ends mount
ed in bearings 178. On one side of the coil 168
are disposed two spiral springs 179 and 180 125
formed of suitable conducting material and hav
ing their outer ends ?xed to terminal bars 181
and
182,
'
'
130
of the coil 168, the other end of coil 168 being
electrically connected to pivot base 175. Upon
cally connected through projection 134, spiral the opposite side of the coil 168 is another spiral 135
spring 133, disc 131, and standard 114, to the spring 183 having its inner end ?xed to the
terminal post 120. Upon the movement of the pivot base 176 and its outer end secured to a ter
movable
coil, the contact arm may engage either minal bar 134. The bearings 178 are supported
-65
of the terminal screws 112 as the current varies in bushings of magnetically permeable mate
between the predetermined limits in the coil. rial disposed in the yoke 175 adjacent portions 140
When the contact arm engages with one of the thereof which are cutaway to receive the spiral
springs 179, 180 and 183, and the pivotal sup
terminal screws 112, a relay 141 will be ener
gized from a battery 142; and when it engages porting means for the coil 168. A cover or cas
with the'other terminal screw, a relay 142 will ing 185 provided for the relay has its edges re
be energized thereby selectively ringing bell 144 ceivable in depressed portions of the base 160 145
or bell 145 from a battery 146 to indicate that
the current in coil 118 has reached one or the
other of the limits of a selected range.
The ends of the coil 118 are connected to
and is secured in place by any suitable means,
such as screws 186 having their ends received
in threaded apertures in the yoke 165.
In Fig. 17 there are shown lead lines 188 of a
circuit, across which the relay is electrically con 150
4
1,927,846
nected. Conductors 189 and 190, which electri
cally connect the terminal bars 181 and 182, re
spectively, with the lead lines 188, have disposed
therein resistance coils 191 and 192, respectively,
for eifecting the desired reduction in energy ap
to move the coil 168 in a counterclockwise di- 5
'rection and will move the contact switch 200 to
the left (Fig. 14), and when the voltage is lower
than that desired, the contact switch will engage
the contact point 201, thus closing the circuit
including the relay 194. The energization of the .
plied to the coil 168. Electrically connected to relay 194 causes the closing of the switch 196,
the terminal bar 184 of the spiral spring 183 is completing a circuit through the indicating sig
a source of current, such as battery 193, for pro
206.
viding electrical energy to switch-actuating re nalReferring
now to Figs. 18 to 21, which show a
lays 194 and 195, the relays 194 and 195 being further modification of the invention, a direct
10 arranged to close switches 196 and 197, respec
current meter 220 is shown mounted in a. casing
tively, when one or the other of two circuits are
15
closed, due to movement of the coil 168. The
closing of the circuits to the relays 194 and 195
is brought about by movement of a pointer or
contact switch 200, which is fixed to the pivot
base 176 and electrically connected to the spiral
spring 183. The upper end of the pointer or con
tact switch 200 may be provided with an indicat
ing dial, but in the present instance there is
shown adjustable contact members 201 and 202
supported by the upwardly extending projection
30
163 of the frame 161 and arranged to be spaced
relative to -the pointer 200. Electrically con
nected to the adjustable contact members 201
and 202 are conductors 203 and 204, which in
clude the switch actuating relays 194 and 195
and form circuits including the battery 193.
The switch 196, when closed due to the energiza
tion of the relay 194, closes a circuit including
221 on a bracket 222 and comprises an external
cylindrical magnet 223 of permanent magnet ma
terial, such as cobalt steel or other suitable per
manent magnetic material, having a pair of pole
shoes 224 secured to the inner periphery thereof
by screws 225. These pole shoes taper outwardly,
as shown at 226, and have a rectangular recess
227 at the base of the tapered portion. A pair 95
of bridges 228'and 229 are adapted to be cen—
tered and secured in the recess 227. The lower
bridge 229 is integral with a ring 231, which fits
in the lower recess 227, while the upper bridge
228 has two ring segments 232 and 233 associated 100
therewith which fit in the upper recess 227 and
accomplish the same purpose as the lower ring
231, the purpose of making the upper ring in the
two segments 232 and 233 being for convenience
in assembling the device. Within the cylindrical 105
space formed by the pole shoes 224 is a fixed per
a signaling means, such as a bell 206; and the manent magnet 234 of cylindrical shape and
switch 197, when closed due to the energization made of cobalt steel or other suitable material
of the relay 195, closes a circuit which includes having a high magnetic remanence and high co
an audible signal, such as a bell 207, a battery
208, or any other suitable source of current sup
plying the electrical energy for these circuits.
ercive force.
The ends of this magnet are re
110
duced, forming a circumferential groove 235 at
either end of the magnet. The inner magnet 234
During the operation of the relay, the coil 168 is provided with pole shoes 236, which extend
is normally urged in a counterclockwise direc circumferentially about the inner magnet, a dis
tion, viewing Fig. 14, by the spiral springs 179, tance co-extensive with the pole shoes 224 se-' 115
180 and 183, so as to move the contact switch cured to the outer magnet; The pole shoes 236
200 to the left and into contact with the contact are retained in engagement with the inner mag
point 201 when the voltage across the line 188 net by a pair of rings 237 which ?t in grooves
is low. However, during the normal flow of provided at the ends of the pole shoes. These
energy, the magnetizing force set up around the rings are provided with partially cut-out por 120
ends of the coil 168 opposes the force of the spiral tions for receiving projections 238 of ring 231 and
springs or, in other words, moves the coil 168 ring sections 232 and 233. These projections ex
a suf?cient distance about its pivots against the tend through the partially cut-out portions of
tension of the spiral springs to centrally position rings 237, between the side faces of pole shoes
the contact switch 200 between the contact points 236 and into the groove 235 of the inner magnet 125
50 201 and 202 and out of electrical engagement to retain the inner magnet securely in position
therewith. If the ?ow of energy is high, the coil and provide a predetermined annular air gap be
168 will be rotated further in a clockwise direc— tween the pole shoes 224 and the pole shoes 236.
tion and in doing so the contact switch 200 will Within this air gap is a movable coil 239 having
be moved into electrical engagement with the journal studs 241 secured to opposite ends there 130
contact point 202, thus closing the circuit in of. These studs carry pivot pins which are jour
cluding the relay 195 which, when energized, will naled in screws 242 mounted in the bridges 228
close the switch 197 in the circuit including the and 229. Each of the bridges is provided with
audible signal 207, indicating that there exists an integral collar 243, which is adapted to re
a high voltage in the main line 188. The audible ceive a resilient or lock washer 244, upon which 135
signal 207 will continue to be energized until the an insulating washer 245 of hard rubber or other
voltage is lowered in any suitable manner. When suitable material is placed. The washer 245 has
the voltage in the main line 188 has been lowered, a collar over which an adjusting lever 246 is
the force of the magnetic ?ux around the coil placed. A second insulating washer 247 is placed
168 will be decreased and the force of the spiral over the lever and the entire assembly is held in 140
springs 179, 180 and 183 will rotate the coil in a place by a locknut 248, which clamps the lever
counterclockwise direction (Fig. 14). Various ad 246 with such compression as to permit its manual
justments may be made to cause the proper volt adjustment. The levers 246 have one end of
age to be supplied in the main line 188, such as spiral springs 251 secured thereto and the other
varying the ?eld of the generator supplying elec ends of these springs are secured to projections
76 trical energy to the main line. The contact 252 secured to the journal studs 241. The pro
switch 200 will remain in a substantially vertical jections 252 are electrically connected to the ends
position as long as there is a desired voltage in of the coil and conductors 253 are connected to
the main line 188, but if this voltage would drop the levers so that the levers serve not only to
an appreciable amount, the force of the spiral adjust the zero position of the coil but also as 150
145
I springs will overcome the magnetic force tending
1,927,346
5
terminals for the electrical circuit to the coil.
The upper journal stud 241 also carries a pointer and spaced therefrom to form an air gap, a mov
254, which cooperates with a scale (not shown)
to indicate the position of the coil, which is an
index of the amount of current flowing through
able coil positioned in the air gap, and means
for supporting said magnet concentrically within
the yoke.
6. An electromagnetic device comprising a cy 80
In this embodiment of the invention the outer lindrical permanent magnet, a cylindrical yoke of
permanent magnet 223 and the inner permanent magnetic material surrounding said magnet and
magnet 237 are magnetized before the assembly spaced therefrom to form an air gap, a movable
of the device, since the magnets must be mag? coilv positioned in the air gap, and means for sup
netized in such a direction that adjacent poles porting said magnet concentrically within the 85
must be of opposite polarity. For instance, the yoke, said means having bearings for c0ncentri~
outer magnet 223 will be magnetized so as to cally supporting the coil in the air gap.
7. An electromagnetic device comprising a cy- ,
have its poles located on a diameter passing
15 through the screws 225. If the pole at the right lindrical permanent magnet, a pair of pole pieces
side of the outer magnet 223, as viewed in Fig. of magnetic material secured to the magnet, a 90
18, is a north pole, the inner magnet 237 willbe cylindrical yoke of magnetic material surround
magnetized to have its south pole at its right ing the magnet and spaced therefrom to form
side. Magnetized in this way, the magnetic ?ux an air gap, a bridge secured to each end of the
20 will ?ow from left to right in two parallel paths yoke and having inwardly extending projections
in the outer magnet and from right to left in a for securing the magnet in position within the 95
yoke, a bearing supported by each of said bridges,
single path through the inner magnet.
and a movable coil pivotally mounted in said
It will be noted that the pole pieces 224, ton bearings.
gether with the entire inner assembly comprising
25
8. An electromagnetic device comprising a cy
the inner permanent magnet?the movable coil
and the bridges form a single unitary structure, lindrical yoke having an axially extending periph~ 100
which may be inserted assembled into the outer
magnet 223. This makes it“ possible to insert a
keeper of magnetic material in the outer magnet
30
along the axis of the poles to retain the magnetism
of the outer magnet after magnetization. The cylindrical magnet
inner assembly may then be inserted in the outer having means for
magnet by pushing the keeper out. In this Way
the device may be assembled with a minimum
demagnetization of the outer magnet.
In each of the embodiments of the invention,
.
the coil.
a source of magneticpotential is provided with
in the movable coil which insures a minimum of
40 leakage ?ux and causes a high torque to be ex
erted on the coil for a given number of ampere
turns in the coil. This high torque makes it pos tatable about said magnet and within the yoke, 1115
sible to use comparatively strong springs for the and a pair of bearings carried by said supports
coils which results in a high degree of accuracy for rotatably mounting said coil.
of the devices.
10. An electromagnetic device comprising a
45
It will be understood that the nature and em. core, a coil wound on the core for producing a
bodiments of the invention herein described and magnetic potential therein, a coil rotatable about E20
illustrated are merely convenient forms of the said core and the coil thereon, and a yoke form
ing a magnetic path externally of the movable
invention and that many changes and modi?ca coil.
tions
may
be
made
therein
without
departing
50
11. An electromagnetic device comprising a
from the spirit and scope of the invention.
core, a coil wound on the core for producing a 125
What is claimed is:
1. An electromagnetic device comprising means magnetic potential therein, a'movable coil sur
for producing a magnetic potential, a coil rotat rounding said core, a yoke forming a magnetic
path externally or" the movable coil, and means
55 able on an axis passing through the coil sur
rounding said means, and a path of magnetic secured to the yoke for positioning the core and.
the movable coil within the yoke.
material externally of said coil.
130
12. An electromagnetic device comprising a
2. An electromagnetic device comprising means
for producing a magnetic potential, a movable cylindrical permanent magnet, a pair of pole
coil,
a support for positioning said means within pieces therefor of magnetic material, a ring of
60
the coil, a support for rotatably supporting the non-magnetic material for attaching the pole
coil on an axis passing through the coil, and a , pieces to the magnet, a cylindrical yoke, means 135
path of magnetic material externally of the coil. secured to the yoke and engaging the magnet, pole
3. An electromagnetic device comprising means pieces, and ring for securing the magnet in posi
tion, and a coil movably supported between the
65 for producing a magnetic potential, a movable pole
pieces and the yoke.
coil surrounding said means, a yoke surrounding
13. An electromagnetic device comprising a 140
the coil, and means for pivotally supporting the
permanent magnet, a movable coil encompassing
said magnet, and a second permanent magnet
forming a magnetic circuit with the ?rst perma
70 lindrical permanent magnet, a cylindrical yoke of
magnetic material surrounding said magnet and nent magnet and positioned externally of the coil.
14. An electromagnetic device comprising a 145
spaced therefrom to form an air gap, and a coil
permanent magnet, a movable coil encompassing
movably supported in said air gap.
5. An electromagnetic device comprising a cy the magnet, and a yoke of a nickel-iron alloy
coil and centering said means within the coil.
4. An electromagnetic device comprising a cy
lindrical permanent magnet, a cylindrical yoke forming a-magnetic path externally of the coil.
15. An electromagnetic device comprising a
of magnetic material surrounding said magnet
permanent magnet, a movable coil encompassing
‘1,927,340
the coil in a predetermined position, and mes-Ill
the magnet, and a yoke of magnetic material associated with each of said springs for variably
forming a magnetic path around the coil and positioning one end of the spring.
shielding the device from external magnetic fields.
25. An electromagnetic device comprising in
16. In a device of the character described, a bar
magnet, a yoke surrounding the ends of said bar
magnet and spaced therefrom to form a rela
tively short air gap, a coil rotatably disposed
around said bar magnet and in said air gap, and
means for urging the rotation of said coil- in one
ner and outer magnetic members forming an air .
gap, a coil rotatably mounted in said air gap, a
10 direction.
1'1. In a device of the character described, a bar
bridge having bearings for supporting said coil.
said outer magnetic member having a ?ange for
receiving the bridge, and an annular member
fitting within said ?ange for positioning the
bridge and thereby centering the coil in the air
magnet, a yoke surrounding the ends of said bar gap.
26. An electromagnetic device comprising in
magnet and spaced therefrom to form a rela ner and outer magnetic members forming an air
tively short air gap, a coil extending around said gap, a coil rotatably mounted in said air gap, a
15 bar magnet and disposed in said air gap, means bridge having bearings for supporting said coil,
for electrically connecting said coil across a cir said outer magnetic member having a ?ange for
cuit supplied with electrical energy, and means receiving the bridge, an annular member ?tting
for urging said coil out of parallel relation to said within said ?ange for positioning the bridge and
bar magnet, the electrical energy supplied to said thereby centering the coil in the air gap, and a
coil setting up a magnetic flux for opposing said projection extending inwardly from said annular
coil moving means for moving the coil in the member for positioning the inner magnetic mem
opposite direction.
the coil.
18. An electromagnetic device comprising a ber27.within
An electromagnetic device comprising a
permanent magnet core, a yoke of magnetic ma plurality of bar magnets in parallel relation, a 100
-25 terial surrounding said core, a pair of pole pieces yoke of magnetic material surrounding said mag
of magnetic material secured to said core and nets and forming air gaps at the ends of said
forming an air gap with said yoke, and a coil magnets, and a coil rotatably mounted so that
rotatably supported in said air gap.
sides of the coil extend into said air gaps.
19. An electromagnetic device comprising a opposite
28. An electromagnetic device comprising a 105
core member of magnetic material, an annular plurality of bar magnets in parallel relation, an
member of magnetic material surrounding the insulating base therefor, a clamp for securing
core, a pair of pole pieces extending from one of
said members toward the other of said members
and forming an air gap therewith, a coil rotat
35 ably supported in said air gap, a pointer movable
with said coil, and a spring for yieldably hold
ing the coil in a predetermined position.
20. An electromagnetic device comprising a
core member of magnetic material, an annular
40 member of magnetic material surrounding the
said magnets to the base, a yoke of magnetic ma
terial surrounding said magnets and forming air
gaps at the ends of said magnets, a pair of stand 11'.)
ards mounted on said base within the yoke, and
a coil rotatably mounted on said standards and
movable in said air gaps.
29. An electromagnetic device comprising a
plurality of bar magnets in parallel relation, an ~ ~
core member, a pair of pole pieces extending from insulating base therefor, a clamp for securing
said magnets to the base, a yoke of magnetic ma
one of said members and forming an air gap with
the other member, a coil mounted in said air
gap, and means for rotatably supporting said
45 coil.
21. An electromagnetic device comprising a
core member of magnetic material, an annular
member of magnetic material surrounding the
core, diametrically opposite air gaps being pro
150 vided between said members, a coil having oppo
site limbs positioned in said air gaps respectively
and pivot-ally mounted for a limited oscillating
movement, the axis of rotation of said coil inter
secting its physical axis at right angles, and a
5.5 pointer carried by said coil.
terial surrounding said magnets and forming air
gaps at the ends of said magnets, said yoke ex
tending over the base and forming a casing for ?
the device, a pair of standards on the base within
the yoke, and a coil rotatably mounted on said
standards and movable in said air gaps.
30. An electromagnetic device comprising a
circular magnet of cobalt steel having poles of 125
opposite polarity at diametrically opposite points,
said magnet having a greater axial length than
radial thickness, pole pieces having surfaces of
similar curvature as the inner surface of said
magnet and engaging the magnet, a cylindrical 130
22. An electromagnet device comprising a core core of magnetic material within said pole pieces
of magnetic material, an annular ?eld magnet and forming a circular air gap therewith, and a
having poles at diametrically opposite points sur magnetically actuated member movable in said
rounding the core, pole pieces of soft magnetic air gap.
31. An electromagnetic device comprising a 135
-60 material'for said magnet positioned at the poles
core
of magnetic material, an annular ?eld mag
. thereof and forming an air gap with the core,
net
having
poles of opposite polarity at diametri
and a coil rotatably mounted in said air gap.
cally
opposite
points surrounding the core, pole
23. An electromagnetic device comprising a
core of magnetic material, a rotatably mounted pieces of soft magnetic material for said magnet
positioned at the poles thereof and forming an
65 coil encompassing the core, a cylindrical magnet
having diametrically opposite poles surrounding air gap with the core, and a magnetically actuat
the core, and a pair of pole pieces having arcuate ed member rotatably mounted in said air gap.
32. An electromagnetic device comprising a
outer faces engaging the inner periphery of the
magnet and forming an air gap with the core for
70 said coil.
24. An electromagnetic device comprising a
magnetic core and yoke forming an air gap, a
coil mounted in said air gap, a pair of pivots for
rotatably supporting the coil, a spiral spring ad
jacent each of said pivots for yieldably retaining
core, a coil wound on the core for producing a
magnetic potential therein, a magnetically actu 145
ated member rotatable about said core and the
coil thereon, and a yoke forming a magnetic
path externally of the magnetically actuated
member,
LELAND E. LAWRENCE.
150