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Патент USA US3092704

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June 4, 1963
3,092,694
S. WALCZAK
LOUDSPEAKER
2 Sheets-Sheet 1
Original Filed Dec. 3, 1956
IN VEN TOR.
SYLVESTER NAI-[ZAK
BY
United States Patent 0 ” "ice
3,692,694
Patented June 4, 1963
2
1
bear and to provide a simpli?ed assembly method for
such a loudspeaker magnetic structure, thereby lower
3,992,694
LGUDSEEAKER
Sylvester Walezak, Egg Harbor City, NJ, assignor to
Radio Corporation of America, a corporation of Dela Q1
ware
Continuation of application Ser. No. 626,011, Dec. 3,
1956. This application Feb. 16, 1959, Ser. No. 793,631
13 (Ilaims. (Q1. 179—115.5)
ing manufacturing costs.
It is another auxiliary object of the invention to provide
loudspeaker magnetic structures that can be assembled
rapidly with a minimum number of rejects and to provide
improved methods ‘for the assembly of such structures.
It is a further object of the present invention to provide
a loudspeaker magnetic structure of high quality and im
The present invention relates to electromechanical and 10 proved performance that is lower in cost than magnetic
structures heretofore available, and to provide an im
electroacoustical transducing apparatus and the methods
proved method of loudspeaker magnetic structure assem
for the assembly of such apparatus, and more particu
bly.
larly to improved magnetic structures of simple and eco
The novel features of the invention, as well as additional
nomical construction for a transducer, such, for exam
ple, as a loudspeaker and the methods of assembly of 15 objects ‘and advantages thereof, will be understood more
such structures and structures of a similar type.
This application is a continuation of my application
Serial No. 626,011, ?led December 3, 1956 and now aban
cloned.
Previous eiforts have been directed toward providing
simple and economically assembled magnetic structures
for loudspeakers. United States Patent No. 2,501,032
discloses a loudspeaker magnetic structure wherein the
fully from the accompanying description when read in
connection with the accompanying drawings, in which:
FIGURE 1 is a fragmentary, exploded view showing,
in perspective, portions of a loudspeaker incorporating a
magnetic structure constructed in accordance with the
invention;
FIGURE 2 is a sectional view, in elevation, of por
tions of a loudspeaker including the magnetic structure
shown in FIG. 1 prior to the ?nal assembly thereof; and
portions of the structure, which de?ne the air gap for re
FIGURE 3 is a sectional view, in elevation, of por
ceiving the voice coil, are accurately positioned with re 25
tions of a loudspeaker including the magnetic structure
spect to each other and anchored in place by means of a
shown in FIG. 1, positioned in apparatus for performing
single member. This member is illustrated in the patent
another step in the assembly thereof.
as a centering ring which surrounds a pole piece disposed
Referring to the drawings, and particularly to FIG. 1
centrally in an aperture in the pole plate of the yoke struc
thereof, there is shown a magnetic structure 2 for a loud
ture. This centering ring centers the pole piece in the
speaker incorporating the present invention. This mag
aperture so as to accurately de?ne the air gap, and is con
netic structure 2 is mounted, for example, by spot weld
structed to exert spring forces on the pole piece so as to
ing techniques, upon a housing 4 in which the diaphragm
anchor it securely in the yoke structure. -In another at
or cone of the loud-speaker will be located. This housing
tempt to simplify loudspeaker magnetic ?eld structure
is referred to in the art as the “dishpan” of the loud
construction, a single strip of magnetic material has been
speaker.
used to form an integral yoke structure and pole plate
The magnetic structure 2 includes a yoke 6 of magnetic
thereby replacing separate pole pieces which are conven
material, such as cold rolled steel. This yoke is shown
tionally fastened to the yoke structure ‘on assembly of
in the drawings as being formed of a band or strip in
the loudspeaker magnetic structure.
Brie?y described, the present invention provides im 40 integral portions. 'I‘hese portions include a pole plate 8,
provements in loudspeaker magnetic structures and im
proved methods for the assembly of such structures.
side plates 10 and 12, and a back plate 14. The band is
formed into a rectangular shell to provide the yoke 6.
The magnetic structure includes a yoke structure that may
The pole plate 8 is fastened to the dishpan '4. This pole
be an integral yoke and pole plate. The portion of the
yoke structure in back of the pole plate is maintained
groove 18 surrounding and concentric with the aperture
initially in open position so that the magnet element of
the magnetic structure, which are enclosed by the yoke,
may be easily inserted therein. This element may in
clude a pole piece which cooperates with the front or pole
plate portion of the yoke to de?ne the air gap. A single
member is provided for positioning the enclosed portion
of the magnetic structure with respect to the yoke so that
it is properly disposed in the air gap. This member is
constructed so as to have spring characteristics.
When
the back portion of the yoke structure is closed, the po
plate has a circular aperture 16 therein and an internal
16. As will be brought out hereinafter, the surfaces of
the aperture 16 will cooperate in de?ning the air gap of
the magnetic structure. The yoke 6 is bent in the form
of a substantially rectangular shell. The shell is closed
except at the corner de?ned by the junction of the side
plate 12 and .the back plate 14. It will be observed that
the back plate 14 is bent at an angle with respect to the
other of the side plates 10. The back plate 14 is initially
disposed above the end of the side plate ‘12. Upon as
sembly, the back plate 14 will be bent downwardly toward
sitioning member is compressed thereby applying spring
the pole plate 8 so as to engage the side plate 12. The
forces to the enclosed portion of the magnetic structure
to anchor the portion in its proper position. Thus, the
are ‘dovetailed so as to lock in place when the structure
engaging ends of the back plate 14 and the side plate 12
magnetic structure and improved assembly methods of 60 is assembled.
The illustrated yoke structure 6 may be formed by
the invention permits permanent assembly in a single
stamping and punching operations. The aperture 16 may
closure operation. The structural arrangement of the
be punched and the groove 18 may be formed in a stamp
parts insures proper alignment of parts and prevents
ing ‘operation. The dovetail parts may be punched. The
over compression of the positioning member. Rejects
dovetail is provided by a tongue on the free end of the
are therefore minimized.
back plate and a groove on the free end of the side plate
It is, therefore, a primary object of the invention to pro
12. It will be appreciated that the principles of the
vide a loudspeaker magnetic structure of simple and eco
present
invention may be incorporated in magnetic struc
nomical construction, and an improved method of as
tures using yokes formed of individual, rather than in
sembly of such structure.
It is an auxiliary object of the invention to provide a 70 tegral portions. It will be desirable, in constructing the
yoke structure 6, to make the height of the individual
loudspeaker magnetic structure combining the features
plates 10 and 12 equal as measured from the pole plate 8
of an integral yoke structure and single centering mem
3
3,092,694
so that the distance over ‘which the back plate 14 travels
when bent on ‘assembly of the structure is limited. In
this manner it will be possible to limit the ‘forces to be
applied to‘the back plate v14 on assembly and prevent
damage to other parts of the magnetic structure 2.
A cylindrical permanent magnet 20 is enclosed within
4
The height of the magnet 2i} and the height of the pole
piece 22, taken together, is such that the pole piece 22
will extend a predetermined distance into the aperture
16 when the magnetic structure 2 is assembled. It may
be observed that any magnet and any pole may be selected
as a pair so long as the sum of the height of the magnet
and of the pole piece are such that the pole piece will
extend into the aperture by the desired distance. For
example, a smaller, shorter magnet may be used with a
the yoke structure 6. This magnet may be of the type
which is constituted of an alloy or aluminum, cobalt,
nickel and iron. A pole piece 22 may be a cylindrical
body of soft magnetic material, such as iron, having a 10 longer pole piece. Any combination of magnet and pole
flange 26 which is disposed in abutting relationship to
piece may be selected consistent with the required mag
the magnet 20. The ?ange 26 forms a shoulder of the
netic characteristics for the loudspeaker. Thus, the incor
body of the pole piece. The pole piece 22 and the mag
poration of the present invention in a loudspeaker increases
net 20 comprise the pole element of the magnetic struc
?exibility in loudspeaker design.
‘
ture. The pole piece 22 is adapted to be inserted into 15
Upon closure of the yoke structure 6, the pole piece
the aperture 16. The peripheral surface of the pole piece
22 will be advanced into the aperture 16 and the mag
22 and inner annular surface of the aperture 16 de?ne an
netic circuit including the yoke structure 6, the magnet
annular air gap for the magnetic structure. This air
20 and the pole piece 22 will becompleted. The distance
gap will receive the voice coil of the loudspeaker.
of this advance Will be determined by the distance of
. The pole piece :22 is desirably accurately centered 20
travel, in a downward direction, of the back plate 14.
Within the aperture 16 in order to accurately de?ne the
This distance of travel is determined by the height of the
air gap. To this end, a centering member 24 of non
side plates 10 and 12. Thus, the height of the magnet
magnetic material, such as phosphor-bronze or brass, is
20 and pole piece 22 is related to the heights of the side
provided. This centering member is in the nature of a
plates 10 and 12 such that the pole piece 22 extends into
ring having a cylindrical side portion or ?ange and a disk
the aperture 16 by the desired distance.
7
like :top portion or Web. The top portion of the centering
The loudspeaker magnetic structure is shown under
member 24 is somewhat corrugated so as to enhance its
going the ?nal step in its assembly in FIG. 3. A press
action as a spring. The centering member 24 functions
30
includes a movable plunger 32 and a support 34 for
both as a centering member and as a compression spring.
‘Consequently, it will be referred to herein as a “comp-res 30 holding the loudspeaker. It will be appreciated that the
press 30 is shown only diagrammatically in order to sim
sion-centering member.” The bottom of the cylindrical
plify
the description of the illustrated embodiment of the
portion of the compression-‘centering member 24 is insert
invention.
ed in the groove .18'that is formed in the pole plate 8.
The support 34 is shaped to receive the bottom of the
Since the ‘groove 18 is concentric with the pole plate aper
dishpan
4. The support 34 is provided with a centrally
ture 16, it provides a seat :for' the compression-centering 35
disposed bore adapted to receive a die 38. The upper
‘member 24, which seat is centered with respect to the
portion of the die 38 is a hollow cylinder. The outer
aperture 16. Thus, the compression-centering member 24
surface of this hollow cylinder has a diameter equal to
is centered with respect to the pole plate aperture v16 when
the diameter of the aperture 16 in the pole plate 8. The
disposed in its seat.’ The unattached end of the .disk por
tion of the compression-centering member 24 bears .upon 40 upper portion of the die 38 projects into the aperture
16 and ?ts between the Walls of the aperture 16 and the
this shoulder formed by the ?ange 26 and by the body of
sides of the pole piece 22; The purpose of the die 38
the pole. piece 22. The shoulder of. the body 26 may be
is to facilitate centering of the pole piece 22.
The plunger 32 of the press 31) includes a holding
A sectional view of the magnetic structure prior to
member 40 having a spring loaded working element 42.
?nal assembly is shown in FIG. 2. The dishpa-n 4 for the
loudspeaker is shown in its entirety in this view. The 45 The working element 42 is mounted ‘for vertical sliding
movement in the holding member 44;“. The working
dishpan '4 isin the nature of a truncated cone. The apex
element 42 is provided with a boss 44 projecting from
of the cone is provided with a large hole substantially
the surface thereof. This boss 44 is adapted to engage
concentric :with the aperture 16. The pole plate 8 oi the
the back plate 14. This boss 44 is located near the side
magnetic structure 2 may be welded to the ‘apex portion
'end of the Working element 42 and engages the free end
of the dishpan 4 :at points around the large hole therein.
of the back plate 14. It will be observed that the back
A strip of metal 28, which projects from the side of the
.plate 14 is bent upon closure and pivots about the cor
dishpan v4, may be provided. A terminal board (not
ner of the yoke structure 6 at the intersection of back
shown) may be fastened to this projecting strip' 28.
The cross-sectional shape of the centering-compression 55 plate 14 and one of the side plates 10. Thus, most
eftcient utilization of forces applied by the press 36 is
member 24 is shown in FIG. 2 as it appears before the
achieved by the application of closing pressure at the
member 24 is compressed and loaded ‘upon assembly of
free end of the back plate 14. The working element 42
the magnetic structure 2. The bottom periphery of the
beveled.’
member 24 rests securely in the groove v1:8 which is con
is spring loaded in order to insure that no greater than
a predetermined amount of force will be applied to the
centric with the aperture '16 in the pole plate 8. The
groove 18 is somewhat wider thanthc thickness of the 60 back plate 14 during the closure operation. The pro
vision of the spring loaded closing element provides fur
member 24 so that the member 24 may be easily inserted
ther insurance against over compression of the center
therein. The shape of the top surface of the member 24
ing-compression member 24.
may be bent in a tortuous manner, as, shown, for pur
poses of improving the action of the compression-center
The ‘assembly of the magnetic structure may be per
ing member 24 as a compression spring. In order to in
formed in a single operation. The open yoke structure
crease the spring torce that will be ‘applied by the center
6;, which has been previously fastened to the dishpan 4,
ing-compression member 24 when loaded, provisions may
is placedupon the support 34 in the press 3%. A guide
be made for increasing the bending moment of the top
46 which forms part of the press 30‘ will be located in
or disk portion of the member 24 about the cylindrical
ternally of the yoke structure 6. The centering-compres
70
sides thereof. To this end, the centering-compression
sion member 24 may be inserted into the grooove 18.
member 24 may be of large diameter in relation to the
The pole piece 22 is then dropped through the hole’ in
size of the yoke 6. The cylindrical sides of the member
the centering member and will be positioned in the aper
24 may also be formed so that they slope inwardly very
ture 16 and in the cylindrical top portion of the die 33.
slightly.
The magnet 20 is then inserted. The guide 46 generally
3,092,694
.5
'
locates the magnet 20 in proper position on top of the
pole piece 22.
With the parts inserted, the plunger 32 of the press
engagement with said magnet element and into assembled
relationship with said side plates.
2. A magnetic structure for a loudspeaker comprising
a magnet element having a pole end of lateral dimension
30 is brought down and closure forces are applied to the
smaller than the lateral dimension of the remainder there
back plate 14. The dovetailed arrangement of the free
of, a centering-compression member having a laterally
ends of the side plate 12 and the back plate 14 engage
disposed web and a longtudinally disposed ?ange, said
so that the yoke structure 6 is permanently enclosed.
web
having an aperture therein of lateral dimensions
Upon closure, the magnet 20 and pole piece 22 are ad
larger
than said pole piece lateral dimension and smaller
vanced. The shoulder 26 of the pole piece 22 engages
the inner rim of the centering-compression member. 10 than said remainder of said magnet element lateral di
mension, said pole end being disposed in said centering
The centering-compression member 24 is therefore loaded
compression member within said ?ange thereof and ex
and compressed upon closure. Over-compression of the
tending through said aperture in said web, a yoke of mag
centering member 24 is prevented since the distance of
netic material including a pole plate having an aperture
downward travel of the back plate 14 is limited by the
height of the side plate 12 which engages the back plate 15 of ‘lateral dimension slightly larger than said pole end
lateral dimension, said yoke also including a pair of side
14. Thus, the magnetic structure may be assembled in
plates, said centering-compression member and said mag
one simple and convenient operation.
net element being disposed within said yoke between said
As an alternative procedure, the parts may be inserted
side plates, said ?ange of said centering-compression
and the back plate partially closed in a ?rst operation
member being disposed on said pole plate of said yoke,
so that the parts cannot come apart from the yoke 6.
Permanent closure can be accomplished in a second oper
ation. Thus, ?exibility in manufacturing techniques is
another feature of the invention. It will be noted that
the number of manipulative steps may be reduced to a
minimum. The anchoring of the elements in a per
manent position is provided due to the forces exerted
by the loaded centering-compression member 24. The
centering-compression member 24 becomes locked into
position against the shoulder 26 of the pole piece 22.
Upon compression, the member 24 exerts spring forces
thereby permanently holding the magnet 20 and the pole
piece 22 permanently assembled in proper relationship.
and means engageable with said magnet element for ad
vancing said pole end longitudinally into said pole plate
aperture and securing said magnet element and centering
compression member in assembled relationship in said
yoke comprising a back plate member for said yoke dis
posed behind said pole plate and movable longitudinally
toward said pole plate into engagement with said mag
netic element and into assembled relationship with said
side plates to complete a magnetic circuit through said
magnet element and said yoke.
3. A magnetic structure for a loudspeaker comprising,
in combination, a cylindrical magnet element having a
pole end with an annular shoulder thereon, a cup-shaped
centering-compression member having an aperture, a
The elements of the magnetic structure 2 are also aligned
in proper operating relationship. Accuracy of the size
yoke of magnetic material including a pole plate having
of the air gap that is de?ned between the cylindrical 35 an annular aperture therein and a pair of side plates
surfaces of the pole piece 22 and aperture 16 is deter
which extend in the same direction from said pole plate,
mined by the centering-compression member 24 and in
said centering-compression member being disposed within
sured through the use of the die 38. It has been found
said yoke on said pole plate and encompassing said pole
that the magnet 26 may be positioned other than co
plate aperture, said magnet element also being disposed
axially with the pole piece 22 without affecting the proper
performance of the magnetic structure. Thus, the guide
46 is merely provided for purposes of convenience of
assembly.
It may be desirable, in order to more ?rmly lock the
back plate 14 to the side plate 12, to incorporate a swag
’ing tool in the press 30. It has been found satisfactory
to swage the sides of the side plate 12 that are near the
ends of the dove-tail joint. Such swaging may be ap
plied to indent these sides of the side plate 12 to the ex
tent shown in FIG. 1 by the dotted lines in the side
‘plate 12.
After the magnetic structure 2 has been assembled on
the press 31}, it may be removed therefrom for insertion
of the cone and voice coil assembly in the conventional
manner.
What is claimed is:
l. A magnetic structure for a loudspeaker comprising,
in combination, a magnet element having a pole end, a
centering-compression member engaged with said magnet
within said yoke with said shoulder thereof disposed
upon said centering-compression member and said pole
end thereof extending through said centering-compression
member aperture and centered by said centering-compres
si‘on member with respect to said pole plate aperture, and
means engageable with said magnet element for advanc
ing said pole end into said pole plate aperture to de?ne
a voice coil air gap and also for securing said centering
compression member and said magnet element in as
sembled relationship within said yoke which comprises a
back plate for said yoke movable in a direction axially
of said magnet ‘element into engagement therewith and
into assembled relationship with said side plates.
4. A magnetic ?eld structure for a loudspeaker com
55 prising, in combination, a cylindrical permanent magnet,
a pole piece having an annular shoulder and disposed at
one end of said permanent magnet, an annular centering
compression member having an aperture therein, said pole
piece extending through said aperture and engaging said
centering-compression member at said annular shoulder,
element and disposed around said pole end, a yoke of 60 said magnet being disposed upon said pole piece and ex
magnetic material having a pole plate and a pair of side
tending axially in a direction opposite to said centering
plates, said side plates both extending in the same direc
member, a yoke of magnetic material having a pole plate
tion, said pole plate having an aperture therein for re
and a pair of side plates, said side plates extending in the
ceiving said magnet element pole end, said centering-com
same direction from said pole plate, said pole plate hav
pression member being disposed within said yoke on said
ing an aperture therein, said centering member, said pole
pole plate, said magnet element also being disposed with
piece and said magnet all being disposed within said yoke
in said yoke with said pole end thereof centered by said
with
said centering-compression member upon said pole
centering~compression member with respect to said pole
plate and extending axially away from said pole plate in
plate aperture to ‘de?ne a voice coil air gap therein, and
means engageable with said magnet element for advanc
ing said pole end into said aperture and securing said
the same direction as said side plates, said centering mem
ber and said pole piece being disposed in centered rela
tionship with respect to said pole plate aperture, and
means engageable with said magnet for advancing said
pole piece into said pole plate aperture to de?ne a voice
magnet element and said centering-compression member
in assembled relationship in said yoke which comprises
a member of magnetic material providing a back plate
for said yoke and movable toward said front plate into 75 coil air gap therein which comprises a back plate for said
3,092,694
7
yoke movable in a direction axially of said magnet into
engagement with said magiet and into assembled rela
tionship with said side plates to complete a magnetic cir
cuit through said yoke, said magnet and said pole piece.
5. A magnetic structure for a iloudspeaker comprising,
8
facing into said pole plate aperture, and then advancing
said back plate into contact with the end of said element
‘opposite said one end to force said one end into said pole
plate aperture against the tension of said centering mem
ber and also into engaging relationship with at least one
in combination, a magnet element having a front end and
of said side plates.
'
>
a rear end, said front end being of smaller diameter than
10. The method of assembling a magnetic structure for
said rear end and having a shoulder, a centering-com
a loudspeaker having: ( 1) a yoke of magnetic material
pression member including a spring~like web and a ?ange,
including a pole plate having an aperture, side plates ex
said web having an aperture, a band of magnetic material 10 tending from said pole plate, and a back plate cooperable
providing a yoke having a pole plate and a pair of side
with said side plates and connected to one of said side
plates integral with said pole plate extending in the same
plates; (2) a magnetic element having one end position
direction therefrom, said pole plate having an aperture,
able in said aperture; and (3) a member having an ape said centering member being disposed within said yoke
ture and also having spring characteristics for centering
with said ?ange on said pole plate and said web spaced 15 said element in said pole plate aperture, comprising plac
from said pole plate, said web aperture being arranged in
ing said centering member on said pole plate between
alignment with said pole plate aperture, said magnet ele
said side plates, placing said magnetic element in contact
ment being disposed in said yoke with said shoulder on
with said centering member with said one end extending
said web and said front-end extending through said web
through said centering member aperture and facing into
aperture in centered relationship with said pole plate 20 said pole plate aperture, then advancing said back plate
aperture, and means engageable with said magnet element
'for advancing said front end of said magnet element into
said pole plate aperture to de?ne a voice coil air gap
therein which comprises an integral part ‘of said band
which constitutes a back plate for said yoke, said back 25
plate and ‘one of said side plates de?ning an acute angle
internally of said yoke with said back plate in engagement
into contact with the end of said element opposite said
one end to force said one end into said pole plate aper
ture against the tension of said centering member, and
?nally engaging said back plate with the other of said side
plates.
11. The method of assembling a magnetic ?eld struc
ture for a loudspeaker'having: (1) a yoke de?ned by a
with said rear end or" said magnet element and in asse i-
strip of magnetic material including a pole plate having an
aperture therein, side plates extending in the same direc
v6. The invention as set forth in claim 5 wherein said 30 tion from said pole plate, and a back plate integral with
bled relationship with the other of said pair of side plates.
pole plate has an annular groove concentric with said pole
one of said side plates along one edge thereof and ex
plate aperture, said annular ?ange of said centering-com
pression member being disposed Within said groove.
tending toward said other side plate, said back plate hav
ing the opposite edge thereof spaced from said other side ,
7. A magnetic structure comprising, a yoke ‘of magnetic
plate; (2) an annular centering-compression member
material having a pole plate, a pair ‘of side plates, said 35 having an aperture therein; and (3) a magnetic element
side plates both extending in the same direction from said
having a pole piece at one end thereof cooperable with
pole plate, and a back plate, said pole plate having an
said pole plate when advanced into said pole’ plate aper
aperture nad a seat centered with respect to said pole
ture'to de?ne an air gap .therein, said method compris
plate aperture, a centering~compression member having
ing placing said member within said yoke, on said pole
an aperture centered therein, said member being disposed 40 plate, and with said pole plate aperture and said center
in said sea-t with said member aperture centered with re
ing member aperture co-axial with each other, placing
spect to said pole plate aperture, said back plate being
said element upon said member with said pole piece ex
, integral with one of said pair of side plates along one of
tending through said centering member aperture, then piv
two opposite edges of said back plate and having one or
otally ‘bending said back plate around said one edge there
a tongue and groove in the'other of its said opposite 45 of toward said other side plate, thereby contacting said
edges, the other of said pair 'of side plates having the
element and advancing said pole piece end thereof
other of said tongue and groove along the edge thereof
into said aperture against the compression of said mem
spaced from said pole plate, said tongue being disposed
in engaging relationship within said groove to form said
yoke, ‘and a magnet having a back end in engagement with
said back plate and a pole end in engagement with said
member and extending through ‘said member aperture
into said pole plate aperture, said member being com
premed by engagement with said magnet and permanently
her, and ?nally engaging said back plate with said other
side plate at said opposite edge of said back plate to
,close said yoke.
12. The method of assembling a magnetic ?eld struc
ture for .a loudspeaker having: (1) a yoke assembly in
cluding a pole plate having an aperture, a pair of side
plates extending in the same direction from said pole
55 plate, and a back plate connected integrally with one of
secured in said seat.
8. The invention as set forth in claim 7 wherein said
said side plates, said side plates, said front plate and back
pole plate has an annular groove concentric with said pole
plate aperture providing said seat centered with respect
to said pole plate aperture, wherein said compression
centerin-g member 11% an annular edge disposed in said 60
plate being integral with each other, the other of said
side plates having a groove therein, said back plate’ hav
ing to tongue cooperable with said groove; (2) a centering
compression member having an aperture; ( 3) a permanent
magnet; and (4) a pole piece having an annular shoulder,
said method comprising the steps of arranging said cen
tering-compression member within said yoke and upon
annular groove, and wherein said member aperture is
‘concentric with said annular edge.
9. The method of assembling a magnetic structure for
said pole plate with said centering-compression member
a loudspeaker having: (1) 'a yoke ‘of magnetic material
including a pole plate having an aperture, side plates ex 65 aperture in alignment with said pole plate aperture, insert
ing said pole piece through said centering member aper
tending from said pole plate, ‘and a back plate cooperable
ture with said shoulder thereof engaging'said centering
with said side plates; (2) a magnetic element having one
member, placing said magnet upon said pole piece with
end positionable in said aperture; and (3) 1a member hav
the axis of said magnet generally paralleling said side
ing an aperture and also having spring characteristics for
centering said element in said pole plate aperture, com 70 plates and with said magnet extending above the end of
said side plates, then bending said back plate with respect
prising placing said centering member on said pole plate
to said one side plate in a direction toward said front
and ‘between said side plates, placing said magnetic ele
'plate into engagement with said magnet thereby advancing
ment in contact with said centering member with said
said pole piece into said pole plate aperture and compress
one end through said centering member ‘aperture and
ing said centering-compression member, and ?nally en
3,092,694
10
said pole piece with the axis of said magnet generally
paralleling said side plates and with said magnet extend
ing above the end of said side plates, then bending said
gaging said tongue in said back plate and said groove in
said other side plate in assembled relationship with each
other.
13. The method of assembling a magnetic ?eld structure
for a loudspeaker having: (1) a yoke assembly including
back plate with respect to said one side plate in a direc
tion toward said front plate into engagement with said
magnet thereby advancing said pole piece into said pole
plate aperture and compressing said centering-compression
member, and ?nally engaging said back plate and said
a pole plate having an aperture, a pair of side plates ex
tending in the same direction from said pole plate, and
.a back plate connected to one of said side plates, said side
plates, said front plate and back plate being integral with
each other, said pole plate having a groove around said
other side plate in assembled relationship With each other.
pole plate aperture and concentric therewith; (2) a cen
tering-compression member having an aperture concentric
with the outer rim thereof; (3) a permanent magnet; and
(4) a pole piece having a shoulder, said method com
References Cited in the ?le of this patent
UNITED STATES PATENTS
prising the steps of placing said centering-compression
member within said yoke upon said pole plate with said
rim in said groove, inserting said pole piece through said
centering member aperture with said shoulder thereof en
gaging said centering member, placing said magnet upon
15
1,941,476
Jensen ________________ __ Jan. 2, 1934
2,046,515
2,174,355
2,501,032
2,524,836
2,666,980
Jensen ________________ __ July 7,
Sundstrom ___________ __ Sept. 26,
Harbough ____________ __ Mar. 21,
Russell _______________ __ Oct. 10,
Russell _______________ __ Jan. 26,
1936
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