Composite armature assembly

A method of manufacturing an armature for a DC motor comprising the steps of: (a) retaining a plurality of armature conductors pre-positioned in a pre-mold position; (b) placing the armature conductors in a mold; (c) adding to the mold a predetermined quantity of soft-magnetic particles, each soft-magnetic particle coated with a non-magnetic material, wherein said particles surround at least a portion of each of the conductors; (d) applying pressure to the mold to affect a compaction molding of the coated soft magnetic particles into a composite structure, wherein the particles and the non-magnetic material form a composite structure armature core substantially encapsulating the conductors within the armature core.

The subject of this invention is related to the subject of United States 
patent application, Ser. No., 08/153,853, filed Nov. 18, 1993, assigned to 
the assignee of this invention and having a disclosure incorporated herein 
by reference. 
This invention relates to an armature assembly for an electric motor 
including a molded composite structure. 
BACKGROUND OF THE INVENTION 
Internal combustion engine cranking motors, such as the type that are often 
found in automotive vehicles, are typically high torque DC motors. 
Armatures for DC motors including high torque motors used as cranking 
motors for internal combustion engines typically comprise a shaft, a stack 
of thin steel sheets called laminations, a commutator and conducting wires 
that are usually copper. In a known method, a lamination stack of a 
specific length is assembled and the motor shaft is mounted into a hole or 
bore axially centered in the lamination stack. Conducting wires are 
assembled or wound in a series of lamination slots. The commutator is then 
pressed onto the shaft and the conducting wires are attached to the 
appropriate commutator bars, completing assembly of the motor armature. 
SUMMARY OF THE PRESENT INVENTION 
Advantageously, this invention provides a new structure for an armature of 
a motor suitable for use in high torque environments, such as for 
automotive cranking motors. 
Advantageously, this invention provides an armature structure that 
eliminates the need for a lamination stack as part of the armature. 
Advantageously, this invention provides an armature structure that can be 
constructed as an integrally molded part. 
Advantageously, this invention provides an armature structure for a DC 
motor that includes a composite material that serves the same function as 
the thin steel lamination stack in prior armatures. 
Advantageously, the armature of this invention comprises a one-piece 
compacted structure that replaces the many pieces of stamped steel 
lamination typically used in an armature assembly. 
Advantageously, this invention provides an armature assembly for a motor 
that is manufactured without need of the steps of stamping, stacking and 
assembling a lamination stack. 
Advantageously, this invention provides an armature structure capable of 
achieving the advantages herein recited comprising a compaction molded 
cylindrical body comprising a plurality of space separated soft magnetic 
particles and a nonmagnetic binder, the cylindrical body comprising an 
axial cylindrical opening adapted for receiving a motor shaft and a 
plurality of conductor openings, parallel to the axial cylindrical 
opening, adapted for receiving a plurality of insulated armature 
conductors. 
Advantageously, this invention provides an armature structure capable of 
achieving the advantages herein recited comprising a plurality of 
substantially U-shaped insulated conductors and a composite core 
comprising a plurality of space-separated soft magnetic particles in a 
non-magnetic binder wherein the substantially U-shaped conductors are 
integrally molded into the composite core and spaced so as to be suitable 
for the creation of armature magnetic fields in a DC motor. 
Advantageously, this invention comprises a method of manufacturing an 
armature for a DC motor comprising the steps of retaining a plurality of 
insulated armature conductors in a pre-mold position, placing the armature 
conductors in a mold, adding to the mold a predetermined quantity of 
soft-magnetic particles each coated with a non-magnetic material wherein 
said particles surround at least a portion of each of the conductors, 
applying heat and pressure to the mold to cause the non-magnetic material 
to achieve at least a partially fluid state, cooling said mold wherein the 
particles and the non-magnetic material form a composite structure 
armature core wherein the conductors are molded in place within the 
armature core and wherein the armature core and conductors comprise an 
integrally molded one-piece structure. 
A more detailed description of this invention, along with various 
embodiments thereof, is set forth further below.

DETAILED DESCRIPTION OF THE INVENTION 
This invention provides an armature for an electric motor comprising a core 
that replaces a lamination stack used in conventional armature assemblies. 
The core is made of a composite material, which is defined as a material 
having a plurality of soft magnetic particles, for example iron particles, 
coated with a non-magnetic binder such as a thermoplastic or resin in 
which the particles are space-separated and bound together by the 
non-magnetic binder. 
In general, the armature according to this invention is constructed 
according to this invention by placing a predetermined quantity of soft 
magnetic particles coated with a non-magnetic binder into a compaction 
mold and compaction molding the particles to form the armature core. The 
armature also includes a shaft to which the core is mounted and plurality 
of insulated conductors that are used in the final motor assembly to 
create the magnetic fields that create motive force in a manner well known 
to those skilled in the art. 
EXAMPLE 1 
Referring to FIGS. 1a-f, a die body 10, having a cylindrical cavity 12, 
receives a predetermined quantity of particles 15 through feed shuttle 14, 
which particles are used in the compaction molding process to form the 
compaction molded composite core according to this invention. Feed shuttle 
14 is adapted to slide across the die body 10 so that, when in the 
position shown in FIG. 1a, particles 15 may be fed into the cavity 12 and 
when in the position shown in FIG. 1b, no particles flow from the feed 
shuttle. 
The process of filling the die body cavity 12 with the compaction powder is 
known as charging and may be carried out as follows. Lower punch 18 is 
raised substantially to the top of the cavity 12 and, as particles 15 are 
fed into the portion of cavity 12 above the top of lower punch 18, lower 
punch 18 is gradually lowered to help "draw" the particles into cavity 12. 
Construction of soft magnetic structures, according to this invention, 
follows the basic steps of known construction of composite iron powder 
structures (see, for example, U.S. Pat. No. 5,947,065, parts of which are 
reproduced below) with additional improvements, according to this 
invention, to provide the resultant structure according to this invention. 
Portions of the following description also appear in the above-mentioned 
United States patent application, Ser. No. 08/153,853, assigned to the 
assignee of this invention. The particles used in the compaction molding 
process comprise particles of iron powder or other ferromagnetic powder 
that, in the end structure, are bound together by an insulating material, 
typically a thermoplastic material. The iron powder in the structure, 
according to this invention, may be Hoeganeas 1000C iron powder. The 
particle size of this powder based on the U.S. standard sieve analysis is 
shown in the following table. 
______________________________________ 
Sieve Percent 
______________________________________ 
+60 1 
-60/+100 14 
-100/+325 70 
-325 15 
______________________________________ 
The particle sizes of the iron powder range from about 44 to 250 microns, 
according to this sieve analysis. However, a very small percentage of the 
powder may have a particle size as small as 10 microns. The powder is 
about 99.7% Fe, 0.003% C, 0.0005% N, 0.006% S, and 0.004% P. The 
thermoplastic material may be an amorphous thermoplastic polyethermide 
resin, an example of which is a General Electric "ULTEM" (Registered 
Trademark General Electric) resin. The thermoplastic material may be 
replaced by a thermoset material, or another alternative material capable 
of performing similar functions. 
To prepare powder for molding, the particles of iron powder are coated with 
a thin layer of thermoplastic material. One way of accomplishing this is 
to mix the thermoplastic material with a solvent to provide a liquid 
material. Another way to achieve the liquid material is with heat, or with 
the use of component liquid materials. 
The powder is then blown by air up through a vertical tube and, at the same 
time, the liquid material is sprayed on the powder to coat the powder. The 
coated powder falls outside the tube and is directed back into an inlet of 
the tube where it is blown up again and coated again. After a number of 
passes through the tube, the particles are all coated to the extent 
desired. The solvent evaporates or is recovered during this process. When 
the iron particles have been completely coated, the quantity of the coated 
particles may be preheated and placed in a heated die body, and/or the die 
body may be preheated. 
During a preferred implementation of the compaction molding described 
below, thermoplastic or thermoset material is heated sufficiently to cause 
it to melt and bond the particles together. Example parameters are as 
follows: compaction mold pressure of 50 tsi (tons per square inch), 
heating temperature of 650 degrees Fahrenheit. 
In the final molded state of the soft magnetic structure, the thermoplastic 
material is bonded to the outer surface of each metal particle so that the 
particles are insulated from each other by thin layers of thermoplastic 
material. Further, the thermoplastic material bonds all the particles 
together to form the composite structure. It will be appreciated that, 
since the particles are separated by the thermoplastic material, there are 
gaps formed between the particles. These gaps act like air gaps, since the 
thermoplastic material separating the particles has about the same 
permeability as air. This air-gap effect increases resistivity and, 
consequently, reduces eddy current loses. 
To provide output performance or power that is comparable to a structure 
that is formed of laminations of steel, the proportions of iron powder and 
thermoplastic material should fall within certain ranges. Thus, by weight, 
the structure should be 95 to 99.9% iron powder and 5 to 0.1% 
thermoplastic. Since about 1% by weight of thermoplastic equal to about 4% 
by volume, a core that is 99% iron powder by weight and 1% thermoplastic 
by weight would be in the range of approximately 96% iron powder by volume 
and 4% thermoplastic material by volume, depending upon the thermoplastic 
(or thermoset) material used. Performance of the iron particles can be 
altered if the iron particles have a phosphorous coating. Thus, the iron 
powder can be coated with a phosphate or phosphorous and this phosphorus 
is then over-coated with the thermoplastic material. When using 
phosphorus, the proportion should be, by weight, 0.05% to 0.5% phosphorus. 
Actuators used in the mechanical compaction molding processes described 
below may be hydraulic, pneumatic, cam operated mechanical, or any 
suitable type of actuator capable of providing the required compaction 
force, and such actuators are readily available to and easily implemented 
by those skilled in the art. 
Die bodies may be preheated, i.e., to a temperature up to 650 degrees 
Fahrenheit to achieve the desired heating of the composite material. Note 
the heating temperatures can vary greatly, depending upon the 
characteristics of thermoplastic or thermoset material used. For example, 
a thermoset material has been successfully used with heating temperatures 
as low as 70 degrees Fahrenheit. Lower and higher temperatures will be 
achieved as new materials are tried. 
The material is compacted at 50 tsi for up to 30 seconds. Good results have 
also been achieved at 45 and 60 tsi. 
The step of preheating or otherwise heating the die need not be utilized. 
However, the resulting composite structure has improved mechanical 
properties when the die is heated or preheated. 
Referring again to FIG. 1a, lower punch 18 is located at the bottom of die 
cavity 12 and is adapted in a manner well known to those skilled in the 
art to slide vertically within the cylindrical cavity 12. Lower punch 18 
has a central axial bore 13 within which is fitted a core rod 16. Core rod 
16 is adapted so that it may slide in the vertical directions within the 
axial bore 13 of lower punch 18, independently of the position of lower 
punch 18. Core rod 16 has an extending portion 17 that extends into the 
cavity 12 of die body 10. 
Referring now also to FIG. 1b, after a predetermined amount of composite 
powder 15 is added to the cavity 12 of die body 10, feed shuttle 14 is 
moved horizontally across the top of die body 10 so that it can no longer 
provide powder to the cavity 12 and so that the composite powder is 
prevented from escaping the feed shuttle 14. Upper punch 20 is lowered 
into the position shown and has a circular cylindrical shape allowing 
upper punch 20 to slidably engage the walls 11 of cylindrical die cavity 
12. As shown in FIG. 1b, the composite powder 15 settles in the die cavity 
12 and surrounds a length of extending portion 17 of core rod 16. 
Referring now to FIG. 1c, the upper punch 20 is lowered into the cavity 12 
and force is applied through a suitable manner, as described above, to the 
upper and lower punches 20 and 18. For example, the force may be provided 
from a hydraulic actuator or an electric motor driven actuator. 
The vertical forces on the punches 18 and 20 are on the order of 45-60 tons 
p.s.i. As upper punch 20 is lowered, the top of core rod 16 slidably 
engages with the central axial bore 22 of upper punch 20. The shape of the 
cylindrical walls of cavity 12 and the top surface 9 and the lower surface 
8 of the lower and upper punches 18 and 20, respectively, determine the 
shape of the armature core being compaction molded. For purposes of this 
example, a substantially circular cylindrical shape is all that is 
required. 
During the application of pressure by the force on the compaction punches 
18 and 20, the die mold 10 is heated (or, alternatively, was preheated) to 
a temperature at which the nonmagnetic binder on the particles of the 
compaction powder 15 becomes at least partially fluid. Application of the 
heat, for example, up to 650.degree. F., depending on the material used in 
the nonmagnetic binder, and the above-mentioned pressure for a time up to 
30 seconds affects a compaction molding of the powder 15 into the armature 
core. After the compaction molding, upper punch 20 is raised clear of the 
die body 10 and lower punch 18 is raised to move the core 19 to the top of 
die body 10, as shown in FIG. 1d, and to disengage the compaction molded 
core 19 from the core rod 16. 
Referring to FIGS. 1e and 1f, a series of U-shaped conductors 26 having 
closed ends 30 and extending leads 28 are provided in a series of holes 21 
in the core 19. The holes 21 may be drilled or molded into the core 19 
parallel to the axial direction in a circular pattern around the central 
axis of the core 19. The core 19 shown has a central axial bore or opening 
23 resulting from core rod 16 in which bore 23 the armature shaft will be 
inserted to complete the armature assembly in a manner easily achieved by 
one skilled in the art. Preferably, while the armature is still hot, the 
shaft is pressed into the armature. As the armature cools, it shrinks 
around the shaft to achieve a firm fit. Alternatively, the shaft may be 
press fit into the armature after the armature has cooled. 
Referring to FIG. 1f, an example armature assembly according to this 
invention, not including the armature shaft and commutator, is shown as 
reference 19' and includes the armature conductors having leads 28 
extending from one end of the core 19' and the closed portions 30 at the 
other end of core 19'. A shaft and commutator (not shown) are assembled to 
the core 19' (shown in 1f) in a manner well known to those skilled in the 
art to complete the armature. The completed armature can then be easily 
implemented into a DC motor assembly according to known manners of 
construction of DC motors. Example shapes and patterns for location of the 
armature conductors 26 are explained further below with reference to FIGS. 
9, 10 and 11. 
Thus, accordingly, this invention comprises an armature structure 
comprising a compaction molded cylindrical body 19' comprising a plurality 
of space separated soft magnetic particles and a nonmagnetic binder, the 
cylindrical body comprising an axial cylindrical opening (reference 23) 
adapted for receiving a motor shaft and a plurality of conductor openings 
or holes 21, parallel to the axial cylindrical opening 23, adapted for 
receiving a plurality of armature conductors 50. 
EXAMPLE 2 
Referring now to FIG. 2, another example motor armature according to this 
invention is shown. The armature 47 shown includes a molded core 46 in 
which is integrally molded conductors 50, such that a majority of the body 
of each conductor 50 is molded into and encased within core 46. Core 46 
retains conductors 50 in place by compaction molding core 46 around the 
conductors 50. Leads 48 extend from the core 46 and are assembled to a 
commutator (not shown) in a manner well known to those skilled in the art. 
The armature 47, shown, core 46 and conductors 50 are integrally molded and 
molded onto the shaft 40 in a single molding process. The shaft 40 has a 
portion (not shown) around which the core 46 is molded and has a first 
bearing end 44 for mounting the armature into a motor housing (not shown) 
and a second bearing end 42 also for mounting the armature into a motor 
housing. 
Referring now to FIGS. 3a-f, an example method of constructing the armature 
shown in FIG. 2 is illustrated. 
Starting with the step shown in FIG. 3a, a die body 10 retains a lower 
punch 40 having an upper end 44 and an axial bore 46. Radially disposed in 
a circular pattern about the axis of lower punch 40 are a series of 
retaining receptacles 42, whose function will be explained below. 
Referring to FIG. 3b, with the compaction molding apparatus placed in the 
position shown, a series of conductors 50 are loaded into the retaining 
receptacles 42 in the end 44 of lower punch 40. The conductors 50 are 
U-shaped, in general, and may be of the type explained below with 
reference to FIGS. 9-11. The receptacles 42 preposition conductors 50, 
retaining each of the conductors 50 in their pre-mold positions. 
The relative location of the conductors 50 is generally that of the final 
position desired for the conductor, examples of which positions are 
described below and variations of which examples will be readily apparent 
to those skilled in the art. During the compaction process, however, there 
may be some radial movement of the conductors 50. Therefore, it is 
desirable that the conductors 50 be placed radially outward of their 
desired final position by a predetermined distance, for example, 0.25 
inches, to account for the radially inward movement that will occur during 
the compaction molding process. It will be seen that the retaining slots 
42 do not allow for radial movement of the ends of conductors 50 and that 
this tends to cause bending, during the compaction molding, of the 
conductors 50 where the conductors 50 extend from retaining slots 42. This 
bending of the conductors during the compaction molding is acceptable. 
Also illustrated in FIG. 3b, a shaft 52 is loaded from a magazine 54 onto a 
loading rod 48. 
Referring now to FIG. 3c, the lower punch 40 is moved downward in the 
vertical direction and the core rod 48 is moved upward so that the shaft 
52 passes through the central bore 46 of lower punch 40 and moves into the 
cavity 12 of the die body 10. Also illustrated in FIG. 3c, the feed 
shuttle 14 moves into the position shown, where the open bottom of the 
feed shuttle 14 is over the cavity 12 of the die body 10 allowing a 
predetermined quantity of compaction powder 15 to be disposed into the 
cavity 12 from the feed shuttle 14 to accomplish charging of the cavity 
12. 
Referring now to FIG. 3d, the feed shuttle 14 has been moved away from the 
opening to cavity 12 and is again in position where it is sealed against 
the top of die body 10. Upper punch 20 is lowered into position and 
engages the cylindrical wall 11 of cavity 12 of die body 10. Core rod 14 
is raised higher, raising armature shaft 52 so that the grooved portion 51 
is properly centered within the conductors 50 and the accumulation of 
compaction powder 15 in the die cavity 12. Grooved portion 51 of the 
armature shaft 52 is included on the shaft to providing a feature 
increasing the bonding strength of the resultant compaction molded core 46 
to the shaft 52. The upper end 42 of the shaft 52 slidably engages within 
axial bore 22 of upper punch 20 as upper punch 20 is lowered into 
position. 
Referring now to FIG. 3e, the die body 10 is heated (or, alternatively was 
preheated) and the compaction punches 20 and 40 are moved in opposite 
vertical directions to apply pressure in the range of 45-60 tons p.s.i. on 
the compaction powder 50 within the die cavity 12 surrounding the proper 
portion 51 of armature shaft 52 and surrounding a majority of each 
conductor 50 (all of each conductor 50 except the extending leads 48). 
This process causes the formation of a solid core that is compaction 
molded and retains the conductors 50 molded in place. The resulting core 
is attached to the shaft 52 by flow of the compaction powder and binder 
into the grooves of portion 51 of the shaft 52. Thus the linear axial 
length of the shaft 52 coextensive with grooved portion 51 is encapsulated 
within the core 46. 
After the part is compacted, upper punch 20 is raised as shown in FIG. 3f 
and lower punch 40 is raised to bring the resultant armature assembly 47 
to the top of the die 10, from which it may be removed to provide the 
resultant structure shown in FIG. 2. 
Thus, as is apparent to those skilled in the art, the above described 
example of this invention is embodied in a motor armature apparatus 
comprising, a plurality of substantially U-shaped insulated conductors 
substantially encapsulated within a composite core, wherein the composite 
core comprises a plurality of space-separated soft magnetic particles in a 
non-magnetic binder and wherein the apparatus also comprises an armature 
shaft having an axially linear portion encapsulated within the composite 
core. 
EXAMPLE 3 
The armature of this invention may be compaction molded using an isostatic 
compaction process such as shown in FIGS. 4a-g. Referring to FIG. 4a, a 
two-piece container comprising lower portion 62 and upper portion 60 may, 
in one example, be fabricated from sheet metal. Other suitable materials 
may be used and it will be understood that this invention is not limited 
to the use of sheet metal in this process. Top portion 60 includes a 
receptacle 64 receiving the top portion of the armature shaft and lower 
portion 62 includes a receptacle 68 for receiving the lower portion of the 
armature shaft. The container lower portion 62 also defines a plurality of 
smaller cylindrically shaped receptacles 66, each having a closed lower 
end and an upper end opening into the chamber defined by body 63. The 
small cylindrically shaped receptacles 66 are radially spaced about the 
axis 61 of the container and adapted to receive and hold in place the 
armature conductors 50. The body 63 of the container will form the 
composite portion of the armature. 
Referring to FIG. 4b, an armature shaft 52 is placed in the lower portion 
62 of the container. A predetermined number of conductors 50 are then 
placed in the lower portion 62 of the container and are properly oriented 
and retained in place by receptacle 66. Next, a predetermined amount of 
composite powder 15 is placed in the lower container 62, filling the 
container. The particles may be added to the container using a vibratory 
powder feeder. The upper portion 60 of the container is then placed on the 
lower portion, which portions are sealed together during the application 
of isostatic pressure, described below, to form a single container 63 
retaining the armature shaft 52, conductors 50 and composite powder 15. 
Referring to FIG. 4c, the container 63 is then placed within an isostatic 
compaction chamber 71 formed in a chamber body 72 having a top 70 for 
sealing the chamber 71 and a hydraulic feed line 74 for receiving 
hydraulic fluid under pressure. 
Referring now to FIG. 4d, after the container 63 is placed in the isostatic 
compaction chamber 71, the top of the isostatic compaction unit 70 is 
placed on the body 72 and sealed. Isostatic fluid 73 is then pumped into 
the chamber through hydraulic line 74. 
Referring now to FIG. 4e, the pressure chamber 71 is heated, through 
heating of the hydraulic fluid prior to its entrance into chamber 71 to a 
temperature sufficient to cause the non-magnetic binder of the composite 
powder 15 to at least partially flow. The hydraulic fluid 73 is 
pressurized to a pressure in the range of 30-55 tons p.s.i. When the fluid 
73 is pressurized, the fluid applies pressure, as represented by arrows 
76, on the container 63 normal to the container surfaces to affect the 
compaction molding of the armature within the container 63, molding the 
composite material around the armature shaft 52 and conductors 50. 
Referring now to FIG. 4f, after the compaction is completed for a time of 
up to 30 seconds at a temperature up to 650.degree. F., or whatever 
temperature is suitable for the binder used, the hydraulic fluid is 
removed from the chamber 71 via line 74 and the top 70 of the chamber is 
removed so that the container 63 containing the compaction molded rotor 
may be removed. 
Referring now to FIG. 4g, the container is then opened destructively so 
that the resultant rotor 47 may be removed. 
EXAMPLE 4 
Referring now to FIG. 5, another example armature assembly according to 
this invention is shown. The armature assembly 90 shown includes a 
compaction molded body 92 containing a plurality of insulated conductors 
50 whose ends 48 protrude from one of the cylinder ends of the body 92 and 
are adapted to be attached to a commutator in a manner well known to those 
skilled in the art. Armature assembly 90 varies from armature assembly 47, 
described above, in that no armature shaft is molded as part of the 
armature assembly. Instead, the armature assembly 90 is molded with a 
cylindrical axial opening 94 extending longitudinally completely through 
the body 92 of the armature assembly 90 and is adapted for receiving an 
armature shaft through a later step of assembly. 
Armature assembly 90 is desirable when a single armature assembly may be 
suitable for use with two or more different armature shaft designs, as 
long as, each shaft design is able to mount the common armature assembly 
according to this invention. 
Referring now to FIGS. 6a-f, an example method of constructing the armature 
assembly shown in FIG. 5 begins with the steps shown in FIG. 6a. The die 
body 10 has a cylindrical chamber within which is slidably engaged a lower 
punch 40. Lower punch 40 has an upper end 44 having a plurality of 
cylindrical receptacles 42 for retaining armature conductors in the manner 
described above. Lower punch 40 has a cylindrical axial bore within which 
core rod 102 is slidably engaged. 
Referring to FIG. 6b, the conductors 50 are mounted within the receptacles 
42 in the upper end 44 of lower punch 40. 
Referring to FIG. 6c, the lower punch 40 is then lowered and the feed 
shuttle 14 is slid over the top of chamber 12 to provide a predetermined 
amount of composite powder into the chamber 12. 
Referring now to FIG. 6d, the feed shuttle 14 is then slid to its original 
non-feeding position so that it is sealed against the die body 10 and 
upper punch 20 is lowered into engagement with the wall 11 of cylindrical 
chamber 12. 
Core rod 102 is then raised through the chamber 12 and into engagement with 
the axial bore 22 of upper punch 20. Core rod 102 prevents the central 
opening 94 of the core body from being filled, thus providing the opening 
into which an armature shaft can later be assembled. 
Referring now to FIG. 6e, the upper and lower punches are brought into 
position and pressure is applied thereto to effect the compaction molding 
of the powder 15 to form the core 46 while molding in place conductors 50. 
During the molding process, the die 10 is heated (or the die 10 may have 
been preheated) to a temperature up to 650.degree. F. After the armature 
has been molded at a pressure in the range of 45-60 tons p.s.i. for a time 
up to 30 seconds, pressure is removed from the upper and lower punches 20 
and 40 and the upper punch 20 is raised and cleared from the die body 10. 
The lower punch 40 is then raised to bring the armature assembly 90 to the 
top of die body 10 and out of engagement with core rod 102, allowing the 
armature assembly 90 to be removed wherein the result is shown in FIG. 5. 
Thus it will be apparent to those skilled in the art that the above 
described example of this invention is embodied in an apparatus comprising 
a plurality of substantially U-shaped conductors substantially 
encapsulated within a composite core, wherein the composite core comprises 
a plurality of space-separated soft magnetic particles in a non-magnetic 
binder. 
EXAMPLE 5 
Referring now to FIGS. 7a-h, a method of compaction molding the armature 
assembly 90 shown in FIG. 5 through isostatic compaction molding is shown. 
Referring to FIG. 7a, the container having two parts 110, 112 is fabricated 
from a suitable material such as sheet metal. The container lower portion 
112 has a body portion 111 within which the compaction powder is placed 
and within which the body of the armature assembly 90 is formed. Lower 
portion 112 includes a plurality of radially spaced receptacles 109 for 
spacing and retaining of the conductors 50. 
Referring now to FIG. 7b, the lower portion 112 of the container is loaded 
with a steel dummy core 114, a plurality of conductors 50 and a 
predetermined amount of compaction powder 15. The upper portion 110 is 
then placed over the lower portion 112 to form resultant container 113 
containing the dummy core 114, compaction powder 15 and the pre-positioned 
conductors 50. 
The container 113 is then lowered into the isostatic chamber 71 as shown in 
FIG. 7c. 
Referring to FIG. 7d, the top 70 is sealed to the body 72 of the isostatic 
chamber 71 and a fluid 73 is fed to the chamber 71 via hydraulic line 74. 
Referring to FIG. 7e, pressure is applied to the fluid via hydraulic line 
74 so that the fluid 73 places isostatic pressure, represented by arrow 
77, against the chamber 113 normal to all surfaces of the container 113. 
During the pressurization, the chamber 71 is heated via heating of the 
hydraulic fluid 73 before the fluid 73 enters the chamber 71. The 
temperature of the fluid may be up to 650.degree. F. or another 
temperature, depending upon the type of binder used. 
After the container 113 has been within the chamber 71 for up to 30 seconds 
at a pressure in the range of 30-55 tons p.s.i. while receiving heat from 
the fluid 73, the fluid is drained from the chamber 71 via line 74 and the 
top 70 is removed from the chamber as shown in FIG. 7f. The container 113 
is then removed and is destructively opened, as shown in FIG. 7g, so that 
the armature assembly 90 is removed. Next, as shown in FIG. 7h, the dummy 
core 114 is removed from the armature assembly 90 to provide the resultant 
assembly 90 shown in FIG. 5. 
EXAMPLE 6 
Referring now to FIGS. 8a and 8b, another example isostatic compaction 
method of manufacturing an armature assembly according to this invention 
is shown. FIG. 8a illustrates a steel base 216 on which is mounted lower 
polyurethane tooling 202. Lower polyurethane tooling 202 is generally 
cylindrical in shape, has a top edge 212 and defines a cavity 208 in which 
the particles 15 are to be added. The inner cavity of lower polyurethane 
tooling 202 also defines receptacle 204 for receiving and retaining in 
place one end of armature shaft 52. A series of elongated cylindrical 
receptacles 206 are radially placed circumscribing the receptacle 204. The 
receptacles 206 are spaced so as to properly locate insulated conductors 
50 as described herein or in any other pattern that may be desired by a 
motor designer. 
To prepare for the compaction molding, shaft 52 is loaded in receptacle 204 
and conductors 50 are loaded in receptacles 206. Next, a predetermined 
quantity of particles 15 are placed in lower tooling 202 and upper 
polyurethane tooling 200, having receptacle 210 for receiving the second 
end of shaft 52, is place over shaft 52 and lower tooling 202. Upper and 
lower tooling 200 and 202 together form a container 201 within which are 
the particles 15, shaft 52 and conductors 50. 
The container 201 is placed within isostatic chamber compaction mold 
machine 218 (FIG. 8b). Machine 218 forms a cylindrical chamber closed at 
one end and open at the other end. When the container 201 is placed within 
the cylindrical chamber through the open end, the steel base 16 acts as a 
wall of the cylindrical chamber to close the chamber. Machine 218 includes 
a means for applying force against the outer periphery of container 201 to 
heat and compaction mold the armature. For example, hydraulic fluid under 
pressure is provided to passage 222, applying the requisite pressure via 
polyurethane diaphragm 220. Pressure can also be applied from cylinder end 
224. The pressure from the compaction molding retains surfaces 212 and 214 
of upper and lower tooling 200 and 202 sealed during the molding process 
and is transferred through the polyurethane diaphragm and tooling to the 
particles 15. Heat for the compaction molding can be provided from a 
preheat of the tooling 200, 202 or from machine 18, including from the 
hydraulic fluid. An example compaction molding pressure is in the range 
from 30 to 55 tsi applied for up to 30 seconds. 
After the compaction molding, hydraulic pressure behind diaphragm 220 is 
reduced and steel plate 216 and container 201 are removed from the machine 
218. The upper and lower polyurethane tooling 200 and 202 are then 
separated and the resultant armature and shaft assembly (FIG. 2) is 
removed from the tooling. 
Machines capable of performing the above described compaction molding using 
the polyurethane tooling 200, 202 are known to and commercially available 
to those skilled in the art and need not be set forth in more detail 
herein. 
Referring now to FIG. 9, an end view of the armature assembly body 92 (or 
19 or 46) provided by any of the above methods of this invention is shown 
with an example radial spacing of the conductors 50 having their ends 48 
revealed and adapted for attachment to a commutator in a well known 
manner. As can be seen, in the example shown, conductors 50 are provided 
in pairs, which increases the current capacity of the armature. 
The examples shown are for construction of a motor armature having a 
diameter in the range of 55-65 mm. The process parameters set forth, 
including the compaction pressure and the compaction time, may vary from 
implementation to implementation depending upon the size of the armature 
fabricated. 
Referring now to FIGS. 10 and 11, an example conductor 50 is shown. The 
conductor 50 has two elongated portions 134 and a closed end 136 to form 
the substantially U-shape. At each end 148 there is a portion 132, 
approximately 10 mm. long, at which end portion 132 insulation is stripped 
from the conductor 50 to allow attachment to a commutator. Further, each 
end 148 terminates in a point 130 as shown. 
The closed end 136 of the conductor includes three major bends, 138, 140 
and 141, as shown. 
Referring to FIG. 11, a profile view of the conductor shown in FIG. 10 
illustrates the asymmetric shape of the insulated conductor 50, which aids 
in the positioning of several closely spaced conductors. 
Referring now to FIG. 12, an example map for the spacing of the conductors 
and mapping of the commutator is shown and can be readily utilized by one 
skilled in the art to guide the spacing and wiring of the conductors and 
commutator. The conductors 50 are spaced so that the resultant armature 
encapsulates a predetermined number, m, of conductors. The m conductors 
are radially spaced about the axis of the armature and are preferably 
positioned so that each conductor, x, substantially overlaps the preceding 
conductor, x-1, and is substantially overlapped by the succeeding 
conductor, x+1. The mth conductor is substantially overlapped by the 1st 
conductor. In most implementations, each conductor will partially overlap 
n other conductors, each to a different degree, where n is less than m and 
greater than 1. The variables n and m will vary from implementation to 
implementation as motor performance requirements vary and can be easily 
determined by those skilled in the art. 
The completion of the electric motor, including the armature of this 
invention, which involves the steps of assembling the commutator and 
placing the motor armature within the motor housing, are easily achieved 
by those skilled in the art and need not be set forth in further detail 
herein. When operating a motor implementing the armature of this 
invention, the motor rpm limit may be set by the strength of the armature 
core according to this invention to retain its structurally integrity 
against forces created by motor rotation. The actual rpm limit will vary 
from implementation to implementation as the armature shape and size 
varies. 
As will be appreciated by those skilled in the art, the above described 
methods of manufacture of this invention are embodied by the process 
comprising the steps of (a) retaining a plurality of armature conductors 
50 pre-positioned in a pre-mold position; (b) placing the armature 
conductors in a mold (FIG. 3, references 10, 20 and 40); (c) adding to the 
mold a predetermined quantity of soft-magnetic particles (FIG. 3, 
reference 15), each soft-magnetic particle coated with a non-magnetic 
material, wherein said particles surround at least a portion of each of 
the conductors; (d) applying pressure to the mold to affect a compaction 
molding of the coated soft magnetic particles into a composite structure, 
wherein the particles and the non-magnetic material form a composite 
structure armature core substantially encapsulating the conductors within 
the armature core. Further, with respect to FIGS. 2, 3a-f and 4a-g, the 
method of this invention additionally comprises the step of prepositioning 
an armature shaft 52 in a pre-mold position, wherein the armature core 
encapsulates an axially linear portion of the armature shaft 52 as shown 
in FIG. 2. 
The above-described implementations of this invention are example 
implementations. Moreover, various other improvements and modifications to 
this invention may occur to those skilled in the art and will fall within 
the scope of this invention as set forth below.