Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to a printed circuit
armature for an electric motor and more specifically for a self-
~ ~ u t a- t i h g
~~~ aommunioatinO D.C. motor.
Various printed circuit armature constructions are
known in ~he art. Examples of such constructions are found in
U.S. patents 3,490,672 (Fisher et al.), 3,512,251 (Kitamori et al.),
3,623,220 (Chase et al.), 3,650,021 (Karol), 3,678,313 (Parker),
3,694,907 (Margrain et al.), and 3,698,079 (Lifschitz). These
known printed circuit armatures generally include parallel con-
ductors with crossover end sec~ions to advance the winding therequired distance. The conductors are formed on the inner and
outer surfaces of an insulating layer with printed circuit
techniques and the layer is shaped into a sleeve and mounted for
rotation about a non-rotatable core~ see Fisher et al. 3,490,672
and Parker et al. 3,678,313.
The present invention relates to a printed circuit armature
for an electric ~otor comprising a cylindrical laminated core of
low reluctance material. An inner layer of insulating aterial
is concentrically bonded to the cylindrical laminated core, the
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inner layer having a plurality of printed circuit conductive
elements arranged on its outer surface. An outer layer of
insulating material is concentrlcally bonded to the inner layer
of insulating material, the outer layer having a plurality of
printed circuit conductive elements arranged on its outer surface,
the conductive elements of the inner and outer layers being
electrically connected.
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In its preferred embodiment the armature includes
two insulating layers bonded to a laminated core with each layer
including a plurality of conductors adhered to a sheet of
insulation. The conductors may be straight or advantageously
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they may be skewed to a maxlmum of about 3. The insulating
layers are bonded together and mounted on a rotatable low
reluctance laminated core. It is used with a motor including
four flat rectangular main magnets symmetrically arranged about
the longitudinal axis of the armature with a pair of main
magnets on each side thereof. A brush is positioned between
each pair of magnets on opposite sides of the armature for contact
with the conductors of the outer layer of the armature so that
the motor i8 self-commutating. The armature, main magnets, and
brushes are enclosed within a suitable housing to form a motor.
The present invention is illustrated in the accompanying
drawings, in which:
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17 FIGURE 1 is an exploded view of a D.C. motor according
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to the present invention, with parts broken away to facilitate
description;
FIGURE 2 is a longitudinal cross sectional view taken
along line 2-2 of Fig. 1 showing the armature; and
FIGURE 3 is a p~ane view with portions removed showing
the printed circuit conductive elements of the two layers.
Referring to Fig. 1, the D.C. motor 10 is shown
including four flat permanent magnets 12, 14, 16, and 18 for
generating a magnetic field B. The magnets 12, 14, 16, and 18
are sandwiched between si~e plates 17 and 19, which serve as
return paths for the magnetic flux. The four flat permanent
magnets 12, 14, 16, and 18 are solid and generally rectangular
in shape.
A cylindrical armature 20 is centrally arranged between
; spaced pairs of magnets 12 and 14, and 16 and 18, respectively,
located on opposite sides of the armature 20. As seen in Fig. 2,
the armature 20 includes a cylindrical core 22, of low reluctance
material, preferably iron, which is concentrically mounted on a
steel output shaft 24. The iron core 22 is formed in a laminated
or segmented structure to reduce hysteresis losses. Preferably,-
the core 22 includes a stack of stamped washers 23, typically
each washer 23 is 12 mils in thickness. Each washer 23 ii8
electrically insulated from adjacent washers 23, e.g., by a film
of varnish or an oxide film.
Referring also to Figs. 2 and 3, the cylindrical
Z6 armature 20 also includes two layers 26 and 28 of spaced printed
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circuit conductiVe elements 30 and 32 bonded to insulating sheets
- 34 and 36. Advantageously, in forming the layers 26 and 28,
conductive sheets are bonded to insulating sheets and the indivi-
dualconductive elements 30 and 32 are formed with the use of
printed circuit techniques, e.g., etching.
With specific reference to Fig. 3, the bottom layer
26 includes 49 conductive elements 30 and has a central or inter-
mediate section 38, in which the individual conductive elements
30 are preferably skewed a maximum of about 3~, and crossover end
sections 40 and 42. The top layer 28 also includes 49 conductive
elements 32, and has a central or intermediate section 44, in
which the individual conductive elements 32 are preferably skewed
a maximum of about 3, and crossover end sections 46 and 48. As
a result of skewing, the conductive elements 30 and 32 in the
:- central sections 38 and 44 of the layers 26 and 28 are oriented
at an oblique angle to the longitudinal axis of the output shaft
24. The crossover end sections 40 and 42, and 46 and 48 provide
the proper circumferential spacing for interconnection of the
conductive elements 30 and 32 of the layers 26 and 28.
In forming the armature 20, the top layer 28 is posi-
tioned over the bottom layer 26 so that the skew of the conductive
elements 32, including crossover end sections 46 and 48, of the
top layer 28 is opposite to that of the conductive elements 30,
including crossover end sections 40 and 42 of the bottom layer 26,
see Fig. 3. Ske~ing of the conductive elements 30 and 32
strengthens the cylindrical armature 20 and reduces the resistance
resulting from interconnecting the crossover sections of the layers
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28 26 and 28.
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The conductive eIements 30 and 32 are formed by etching
thin copper sheets, prefera~ly about 3 mils ~o about 5 mils in
thickness which are bonded, e.g., by epoxy, to fiberglass insu-
lating layers 34 a~d 36. Advantageously, the conductive elements
32 of the top layer 28 may have a thickness of ahout 5 mils and
the conductive elements 30 of the bottom layer about 3 mils. The
two layers 26 and 28 are blanked to the outline of the conductQr
pattern and then bonded together, e,g., with epoxy, and formed
into a cylinder of proper dimensions on a mandrel.
An outer layer or sheath 50 of insulating material,
such as fiberglass thread, may be bonded, e.g. with epoxy, to
the outer layer 28 to further reinforce the cylindrical shape of
the armature 20. A central of intermediate portion 52 of the
outer sheath S0 is removed to provide a gap for exposing the
conductive elements 32 of the central section 44 of the top layer
28.
The crossover end sections 40 and 42, and 46 and 48,
of layers 26 and 28, respectively, are interconnected, e.g., by
soldering or welding. The completed outer armature tube 4g is
xemoved from the mandrel and bonded to the ixon core 22, e.g.,
with epo~y.
In forming the completed motor 10, a pair of bea~in~
spacers 54 and 56 are concentrically mounted on the shaft 24
adjacent the ends of the iron core 22. Bearings 58 and 60 are
mounted on the shaft 24 adjacent the bearing spacers 54 and 56,
respectively. A ring washer 62 having a diameter equal to 1:he
27 dia~eter of the iron core 22 is arranged between bearing spacer
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54 and bearing 58. A spring washer 64 is positioned on the side
opposite to the ring washer 62 in contact with the outer race
of bearing 58, and flat washers 68 and 70 are positioned between
the inner races 72 and 74 of bearings 58 and 60 and the ring
washer 62 and bearing spacer 56, respectively. The bearings 58
and 60 have their inner races 72 and 74 bonded to the output
shaft 24 and their outer races 75 and 76 bonded to end plates
78 and 80.
The end plates 78 and 80, which are preferably made
of aluminum, are mechanically coupled to the side plates 17 and
19, e.g., with screws (not shown) to hold the motor 10 in an
assembled condition. The end plates 78 and 80 include axially
aligned apertures 82 and 84 which receive the ends of output
shaft 24. Enlarged recesses 86 and 88 in the shape of stepped
cylinders are arranged in the end plates 78 and 80 concentric
with the apertures 82 and 84 to receive the bearings 58 and 60,
and poxtions of bearing spacers 54 and 56. Side plates 17 and 19 ;
include arcuate channels 89 and 89a for rotation of the armature
20 within the assembled motor 10.
Centrally arranged on opposite sides of the armature
20 and positioned between adjacent magnets 12 and 14, and 16
and 18, respectively, areopposing brushes 90 and 92. The brushes
90 and 92 are solid and rectangular in shape and biased for con- ;
tact with the exposed conductive elements 32 of the top layer 28 '
of the armature 20 by springs 94 and 96, respectively. ~he
springs 94 and 96 have one end mechanically coupled to contact
terminals 98 and 100 and their other end engaging brushes 90 and
28 92.
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The assembled motor 10 may also include four rectan-
gular spacing strips 102 which may be made of rubber. The
spacing strips 102 are positioned adjacent the magnets 12, 14,
16, and 18 at the outer end thereof and have one end in contact
with the contact terminals 98 or 100 and their other end in
contact with end plates 78 or 80. It may be advantageous in
some applications, e.g., where reduction of magnetic leakage is
desired, to replace the spacing strips 102 with edge magnets.
In operating the motor 10, main magnets 12, 14, 16,
and 18 set up amagneticfiëIdB in the direction indicated by
the arro~ marker B. A d.c. current (I) is applied to the
terminal 100 and carried by brush 92 to the outer conductive
elements 32 in contact therewith. The current travels through
these outer conductive elements 32 and as a result of the inter-
connection o the conductive elements 30 and 32 through certain
of the inner conductive elements 30, and back through the outer
conductive elements 32 in contact with brush 90 and through
brush 90 to terminal 98, completing the circuit.
According to basic electromagnetic theory, a ~orce
is applied to the individual conductive elements 30 and 32 of the
armature 20 due to the interaction of field B and the current I
passing through the conductive element~ 30 and 32. The ~ector
equation F = IL x ~ defines the force acting upon each of the
conductive elements 30 and 32 of the armature 20 through which
the current passes. These forces cooperate to apply a force
couple to the armature 20 causing rotation of the armature 20
27 and shaft 24 at a speed dependent upon the length of the -~
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conductive elements 30 and 32, the strength of the magnetic
field B and the magnitude of the current I.
It should be understood by those skilled in the art
that various modifications may be made in the present invention
without departing from the spirit and scope thereof as
described in the specification and defined in the appending
7 claims.
This application is a divisional application of
Canadian application serial number 225,146, filed April 22, 1975.
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