Note: Descriptions are shown in the official language in which they were submitted.
~Z2694
E. Barber - 3/~
BACKGROUND OF THE INVENTION:
. _ . .. .. .
The general construction of a transducer such as a
conventional bi-polar receiver, called generically a central
armature receiver, is shown by U.S. Patent 3,439,130 issued
April 15, 1969 to A. J. Chase et al. In that patent, the
magnetic subassembly is fabricated on an insulating terminal
block which seats within a frame of generally tubular section.
Magnetic pole pieces, generally of the shape shown by the
patent, may be employed in the present invention.
Customarily in structures such as that of the cited
Chase et al patent, the pole pieces are affixed within the
terminal block and ground by precision tooling to align the
pole tips and space them precisely relative to the block for
joinder to the armature and diaphragm assembly.
Air gap adjustment of the conventional type is also
shown by U.S. Patent 3,542,974 to Blastic et al as issued
November 24, 1~70.
SUMMARY OF THE INVENTION:
The present invention is directed to an improved
structure for the magnet and pole piece assembly of a tele-
phone transducer and to an improved method of adjusting the
air gap between assemblies while joining the assemblies into a
transduce~.
The magnetic structure may in one form include a
permanent bar magnet interposed between the crossbar of
identical T-shaped pole pieces. The legs of the pole pieces
extend through openings in respective coil bobbins and extend
through slots in the base of the assembly housing. The pole
piece legs terminate in pole faces or pole tips of desired
--2--
~lZ2694
E. Barber - 3/4
flatness and alignment. The pole faces confront an armature
across an air gap, the acoustic properties of the resulting
transducer largely being a result of the proper alignment and
positioning of the pole faces and their spacing from the
confronting armature.
A second form of the invention uses a ring magnet.
A central pole member is force-fitted into a disc designed to
rest on the magnet. The ring fits through a slot in the cup to
mate with the magnetic plate during assembly. The central
pole face extends within the ring opening and aligns itself
with the magnetic plate and the ring in a similar manner.
The invention is further directed to improved
structure for producing desired air gap spacing between the
magnetic assembly and the armature assembly in an economical
manner.
The present invention provides an improved magnetic
structure which can readily and economically be assembled, and
a method for assembling and adjusting the air gap of the
transducer.
The structure of the present invention provides a
terminal block in the form of a cup housing. The housing
cavity has aligned spacing and nesting ribs enabling the drop-
in assembly of coils, pole pieces and permanent bar magnet.
The nesting ribs align the pole pieces so that their pole tips
protrude freely through slots in the cup base. By placing
these pole faces in magnetic engagement with a magnetic plate,
the positioning and alignment of the tips can be per~ormed
precisely as part of the assembly process in a simple and
economical manner. By holding the engagement while the cup is
filled with potting compound, the pole face tips are set into
permanent alignment in a common plane.
--3--
~lZ2694
E. Barber - 3/4
The positioning of the pole tips, relative to the
cup housing, may be in a common plane coincident with the cup
base, may be in a plane above the cup base or a plane below the
cup base. In this way, the plane of the pole tips will in a
plane parallel to or coincident with that of the cup base. By
this process, the need for grinding the pole tips to assure a
parallel relationship with each other and the cup base is
totally eliminated. The same relationship can be attained
with a ring magnetic member comprising one pole tip and a
central coaxial rod forming the second pole tip, where the rod
has mounting structure floatingly resting on the upper extent
of the ring magnet.
It is therefore an object of the invention to
provide a new and improved magnetic assembly for a telephone
transducer which can be assembled and adjusted simply and
economically.
It is a further object of the invention to provide a
structure for receiving the magnetic components of a telephone
transducer in a drop-in manner, for simple adjustment,
alignment and securing the resulting magnetic assembly in a
unitary manner.
It is a ~till further object of the invention to
provide a new and improved method of assembling and adjusting
the magnetic air gap of a telephone transducer.
BRIEF DESCRIPTION OF THE DRAWINGS:
~ . . . _ . , _ . .
Figure 1 is a plan view partially broken away of the
magnetic assembly of my invention î
Figure 2 is a sectional view taken along lines 2-2
of Figure l;
--4--
~L~ZZ694
E. Barber - 3/4
Figure 3 is a plan view of the cup of Figure l;
Figure 4 is a side view, half sectioned of the cup
of Figure 3;
Figure 5 is a bottom view of the cup of Figures 3 and
4;
Figure 6 is a side view in section of one type of
diaphragm assembly usable with the magnetic assembly of
Figures 1 and 2;
Figure 7 is a side view in section of a second type
of diaphragm assembly usable with the magnetic assembly of
Figures 1 and 2;
Figure 8 is a side view in elevation of a pole piece
as shown in Figures 1 and 2;
Figure 9 i5 a plan view of the pole piece of Figure
3;
Figure 10 is a side view partly in elevation and
partly in section of a cap as used in Figures 1 and 2; and
Figure 11 is a plan view of the cap of Figure 10.
DETAILED DESCRIPTION OF T~E INVENTION-
In Figure 1, I show a magnetic assembly 10 of atransducer of the type preferably adapted for use in a mag-
netic telephone tran~ducer.
The assembly 10 is comprised of a housing or cup 12
into which are inserted magnetic coils 14, pole pieces 16, and
permanent magnet 18. A cap 20 is held in covering relation to
the cup enclosing its contents. The interior of the cup may be
filled with a potting compound suitable for encapsulating
electrical components and assemblies.
~2~694
The cup 12 is shown in greater detail in Figures 3-5. The cup may
be molded of suitable plastic material having superior dimensional stability. A
typical material which could be used is that sold under the trade name Noryl.
The cup has an outer generally cylindrical wall 30 stepped inwardly
intermediately along its height to an externally threaded section 32. The cup
is essentially tubular with an inner generally cylindrical cavity 34 whose
bottom e2~tent is defined by the extent of the integral cup base 36. The cup
base is otherwise imperforate but has two spaced rectangular slots 38 to
communicate between the cup cavity and an inset 40 below the base as seen
best in Figure 2 and 4.
As best seen in Figures 3 and 4, the cup has opposed screw-
receiving sockets 50 in the upper surface of the side-wall 30, as will be
explained.
The cup cavity is generally cylindrical and has pairs of opposed ribs
upstanding in the cavity to form drop-in nests for the inserted components as
previously noted.
Two pairs of spaced ribs 52 form the partial side-walls to receive
and position the two electrornagnetic coils 14. The wall of the sockets 50 also
act to position the coils on the cup base 36, or on a gasket or spacer 54 resting
on the cup base 36. The ribs 52 have rectangular offsets 56 at their inner ends
for supporting thereon the arms 60 of the T-shaped pole pieces 16. The pole
piece arms 60 are symmetrical about the pole tip 62, the pole tip sized to pass
through base slots 38 as the arms rest on offsets 56. The pole pieces are
fabricated of a suitable nickel alloy conventionally used in telephone
transducers,
~ .
~ 2694
E. Barber - 3/4
The permanent maynet 18 is inserted between the pole
piece arms on the top of the bobbin of the coils 14 with ribs
64 acting to position the magnet 18, as seen best in Figure 1.
Thus, the cavity has ribs 52 and 64 configured to
properly position the seal 54, coils 14, pole pieces 16 and
permanent magnet 18 within the cavity by drop-in insertion.
As mentioned, with the pole pieces passing through
the cup base slots, the pole piece cross arms rest on the rib
offsets 56. The pole tips may and preferably should extend
below the plane 70 defined by the bottom surface of sidewall
30 with the pole faces 72 essentially parallel to the plane
70.
With the coils, pole pieces and magnet assembled
into the cup, the cup is placed on a metallic plate 74 of
magnetically retentive material, the cup resting along the
plane 70. The pole tips 62 engage the surface of plate 74 and
are attracted to the plate with a firm hold. The pole tips are
thus held with their pole faces 72 parallel to the plane 70.
As shown, the pole faces will be in plane 70. If desired, the
pole faces could be held above plane 70 by the use of shims or
spacers, or could be below plane 70 by resting the cup side-
wall on a suitable spacer. For simplicity and convenience in
assembly, the approach shown of having the pole faces 72 in
plane 70 has been adopted. This approach allows the cup to be
placed directly on plate 74 without the necessity of locating
the cup relative to spacers and the like.
With the cup on the magnetic plate 74 and the pole
faces 72 attracted to the plate, the pole cross arms will rise
above the offsets 5~ and the coil bobbins. The permanent
-7-
Z2694
E. Barber - 3/4
magnet and pole cross arms will be held in a magnetic circuit
completed by the magnetic plate and will be firmly held in
place.
Cap 20 may then be fitted to cover the cup cavity
34. The cap 20, seen best in Figures 2, 10 and 11, has a
rectangular cover 82 and a stepped circular flange 84 with
opposed semi-circular cutouts 86 for the terminal screw
sockets 50. The flanged portion 84 has four slots 88 for
receiving the respective horizontal terminal tips 90 of the
terminal 9~. Wires from the coil bobbins may be connected to
the terminal tips at any intermediate stage in a conventional
manner. The cap is set onto the top of the cup, the terminal
92 is set onto the cap with the horizontal tips 90 extending
through the slo~s 86.
The assembly is then ready for the introduction of
potting compound into the cup cavity through the opening 96 in
the cap. ~ny air drying potting compound suitable for
electrical or electronic component use such as epoxy may be
injected or otherwise introduced into the cavity 34 through
the injection opening ~6. As the compound hardens or sets,
the magnetic circuit (including the pole faces to magnetic
plate attraction) remains intact and the relative positioning
of the pole faces relative to the magnetic plate remains
constant. When the potting compound has hardened, the
assembly may be removed from the magnetic plate and the pole
~aces will remain in the plane parallel or coexistent with
that of plane 70.
--8--
~ZZ694
E. Barber - 3/4
In Figures 6 and 7, I show two alternate forms of
diaphragm/housing assembly into which the magnetic assembly 10
may be further assembled. In Figure 6, the housing assembly
110 includes a non-magnetic outer housing 111 of concentric
cylindrical tubular sections 112, 114 and 116 and having an
inner female threaded section 120. A disc armature 122 is
held by a diaphragm 124 in position adjacent section 120. A
protective screen or perforate grid 130 may be used to cover
the armature from its exposed side in a known manner. The
diaphragm and grid may be held in place by any conventional
means such as crimping or swaging the edge of the lower
section over the outer periphery of the grid. Alternatively,
the diaphragm may be held by shoulder 132 between stepped
sections 114 and 116 to hold the diaphragm from inward axial
movement without crimping.
In either form, the threaded section 32 is inserted
into female threaded section 120 of the housing 111 and is
tightened until the air gap between the magnetic pole faces 72
and the armature 122 is of a desired level. The adjustment is
made by monitoring the acoustic output of the transducer on a
suitable instrument as the magnetic assembly i5 advanced into
the housing a~sembly by the mated threads until a desired
response level is achieved. At that response level, adhesive
previously applied to the threads is allowed to harden and set
the air gap at the desirecl level. At this point, the terminal
screws 94 and a varistor may be assembled if required for a
particular application of the transducer.
~ZZ69~
E. Barber - 3/4
In Figure 7, a transducer such as a receiver housing
140 of another configuration is used, that normally designed
for use in the handset of a conventional telephone. The outer
cylindrical wall 142 of the housing is of one diameter on
intermediate arcuate web 144. The inner threaded bore 146
from the outer wall, the inner bore being sized to mate with
and receive the threaded section 32 of the magnetic assembly
10, in the manner previously described for the receiver
housing of Figure 6. In both the embodiment of Figure 6 and
that of Figure 7, the position of the magnetic pole face and
armature are held within their respective assemblies against
axial movement by construction members of that assembly or
module. During the screw adjustment, the air gap may be set.
The adhesive on the threads holds the magnetic assembly module
to the armature assembly module to thereby set and permanently
fix the air gap at the desired setting.
By the use of the construction as set out, a
magnetic assembly can be readily completed using drop-in parts
which fit into nesting members within a cup-shaped housing.
The magnetic structure is held magnetically in proper align-
ment and positioning without the need for subsequent adjust-
ments and/or after assembly grindings. With the magnetic
structure alignment held magnetically, the alignment and
position may be set and fixed~ The fixed position is main-
tained by the set of a potting compound introduced into the
cup and allowed to harden as the pole face position is held
magnetically. The completed magnetic assembly may be mated
with a housiny assembly while adjusting the air gap in the
manner disclosed thereby to complete the receiver.
--10--
~1;22694
E. Barber - 3~4
The drawings of the present invention show an arma-
ture with separate pole pieces. It should be noted that the
air gap ajdustment technique may also be performed with a ring
pole face as the output member of the magnet assembly for
joinder to the armature assembly. With this magnetic struc-
ture, a single slot is provided in the cup. The ring rests on
the lip of the cup to position the annular pole tip beneath the
cup slot. A central pole piece is force-fitted into a disc,
the disc rests on the ring magnet above and spaced from the
annular pole piece. The central pole piece extends within the
cavity of the annulus. By completing a magnetic circuit
between the tips of these pole fa_es, the pole tips can be
aligned in relative positions which can be set, as described
previously.
