Note: Descriptions are shown in the official language in which they were submitted.
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SUBMERSIBLE h'LECTRIC MOTOR
AND METHOD OF ASSEMBLING SAME
Background of the Invention
1. ~ield of the Invention
This invention relates to a roll-formed,
submersible electric motor for a well pump wherein
motor laminations are compressed between an end ring
and a coupling base while an outer metallic shell is
formed to grippingly engage the ring and base,
thereby maintaining the components in assembled
relationship. The coupling base has fluid conduits
for circulation of coQlant to an armature bearing,
and the base also has structure for contacting one
end of a stack of pump stages and maintaining the
latter in aligned relationship to the pump drive
shaft.
2. Description of the Prior Art
Construction of a reliable, efficient
submersible electric pump motor has long been a
challenge reserved for the most experienced engi-
neers. The motor must be designed to easily fit
within ~he confines of four inch well pipe, yet must
develop the required horsepower with high effi-
ciency, low power consumption and long term depend-
ability. The stator must be completely encapsulated
to preclude infiltration of water under high pres-
sures encountered in deep wells. Moreover, the
various components are desirably resistant to cor-
rosion, impact, and infiltration of water-carried
abrasives, the latter of which could lead to bearing
failure in a relatively short period of time.
In the pa~st, submersible electric motor
stators were commonly assembled by a procedure
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1 wherein a series of flat, ring-like laminations is
securely interconnected by cleats or straps. The
laminations and a plurality of stator windings are
inserted between a cylindrical stator liner and an
outer motor shell. A top and bottom end ring are
resistance welded to the liner and shell, and epoxy
is injected in an attempt to fill voids around the
laminations and windings.
The upper end of a typical prior art
motor has a shouldered cast iron bearing housing
received in the bore of the upper end ring, and a
pump-motor coupling base is bolted to the upper ring
and complementally engages the bearing housing for
retaining the latter in general alignment with the
motor shell. Also, the base is connected to an end
member of a separable pump assembly comprising a
plurality of pump stages disposed in stacked rel~-
tionship between the end member and an upper dis-
charge head.
Unfortunately, such prior art motor assem-
blies inherently present difficulty in alignment of
the armature bearings. Initially, the upper and
lower end rings need be maintained in parallel and
coaxial alignment during welding of the outer shell
and inner stator liner to the rings. Subsequently,
the bore of both of the rings must be machined for
axial alignment and the end faces of the rings must
be machined for parallelism. Furthermore, both of
the bearing housings must be machined at their
outer, ring engaging peripheries as well as their
inner bores. Obviously, this multiplicity of the
various machining operations results in an additive
buildup of tolerance limits such that each o the
machining operations~must be precisely kept within a
relatively small, specified error limit.
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Moreover, machining of such motor assem-
blies is rendered difficult by ~he size of the outer
motor shell in relation to the laminations. Such
laminations are of a diameter somewhat smaller than
the inner diameter of the shell in order to easily
insert the laminations within the shell during
assembly. However, during injection of the encap-
sulating epoxy in the voids surrounding the wind-
ings, some of the epoxy might fill a portion of the
10gap between the outer edge of the laminations and
the shell, while in other areas of the motor, little
or no epoxy might flow into the gap between the
laminations and the shell. As a result, the exter-
ior surface of the motor shell cannot be satisfac-
15torily gripped during machining of the bore and face
of the end rings since the partially filled gaps
between the laminations and the shell precluded
- assurance of perfect circularity of the shell and
subsequent àlignment of the clamping apparatus with
20the desire`d bore location of the end rings. In-
stead, past practice mandated the use of relatively
complex, interior clamping mechanisms which expanded
to grip a recess within the motor end rings during
boring and facing of the latter.
25The gap between the edge of the laminations and
the shell of prior motors, however small, also
required the use of a separate connection for insur-
ing ground continuity between the lamina~ions and
the outer shell. Needless to say, there is a long
felt need in the art for a pioneering advance in the
science of motor construction so that the numerous
disadvantages as outlined hereinabove can be avoid-
ed,
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Summary of the Invent _
The roll-formed motor of the instant
invention represents a significant advance in the
art not only by presentation of numerous novel
components but also by means of unique methods of
assembly. In fact, it has been found that the cost
of manufacturing the instant motor assembly and its
associated p~mp is reduced to approximately the same
expense that would be incurred by replacement of the
motor alone in a malfunctioning, prior art pump and
motor assembly.
In more detail, a motor end ring and a
coupling base are provided which both have a cylin-
drical projection directly engaging opposite ends of
a stack of laminations. The end ring, the base and
the laminations are press fit into an outer motor
shell which is then roll-formed to grippingly engage
- complemental shoulders on the ring and base. Also,
a stator liner is slidably inserted into recesses in
the end ring and base and is provided with O-rings
~ for precluding water infiltration.
The provision of cylindrical projec~ions
on the base and the ring for engaging opposite ends
of the stack of laminations enables the base and
ring to be maintained in axial alignment with the
laminations. Once the motor shell is formed to
engage the shoulders on the base and the ring, the
shell is operable to thereafter retain the projec-
tions in engagement with the laminations and conse-
quently thereafter retain both the base and the ring
in alignment with the laminations, thereby simpll-
fying the task of aligning the armature bearings to
the stator.
The stator liner, which is slidably in-
serted in a recess in the end ring and a recess or
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.
1 groove in the base, need not be precisely po~itionedduring assembly of the motor. Assembly is thus
facilitated in comparison to prior art motors where
in the stator liner must be held in precise coaxial
relationship to the end ring and base as the liner
is welded to the same.
The stack of laminations is held in com-
pression between the projections on the base and the
end ring as the motor is assembled. Thereafter,
once the outer shell is formed to complementally
engage the ring and base, the shell exerts tensile
forces against the base end ring to maintain the
laminations in compression. Thus, the need for
cleating or straps to retain the laminations in
stacked relationship during motor assembly is elimi-
nated.
The outer, cylindrical surface of the
lamination stack has a diameter substantially equiv-
alent to the`inner diameter of the motor shell.
Thus, the shell directly engages each of the lamina-
~ tions to substantially preclude shifting of the
laminations in a transverse direction relative to
the stack. Advantageously, the laminations are of a
diame~er such that the latter must be pressed under
pressure into the shell during assembly to insureintimate, mating contact with the shell and thus
provide a continuous grounding structure for the
motor. Furthermore, elimination of the gap between
~ ` the laminations and shell as found on prior art
motors enables the outer shell to be gripped
directly by a clamping mechanism for ease of machin-
ing the end faces and bores.
The coupling base is an integral assembly
which directly connects the mo~or to the pump. The
base is provided with a second shoulder aligned but
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1 spaced from the shoulder engaging the motor shell,
so that the second shoulder may be utilized for
grippingly engaging a complementally formed pump
casing and thereby retaining the latter in aligned
S relationship with the shell. Additionally, the
upper end of the coupling base directly contacts the
lower stage of the pump staging stack so that the
base is thus operable to align the staging relative
to the position of the casing.
The base is molded to directly contact and
securely support a sleeve bearing for an armature
without the use of a bearing housing or the like.
Thus, the bearing, in place in its ultimate disposi-
tion, can thereafter be machined for exact concen-
tricity and parallelism to the laminations, the
shell as well as the bearing housing bore at the
opposite end of the motor. The elimination of the
upper bearing housing in conjunction with an upper
end ring thereby eliminates two machining operations
(that is, the machining of the outer housing surface
- as well as the complemental housing receiving bore
in the ring) and consequently positional tolerances
of the upper bearing to the lower bearing can be
maintained at low limits.
The synthetic resinous coupling base is
provided with a plurality of fluid conduits communi-
cating with the outer surface of the armature sleeve
bearing- for enabling the circulation of coolant to
the bearing during use. The large, cast iron bear-
ing housing of prior art motors absorbed thermal
energy from its associated bearing and conductively
transferred the same toward the end ring and outer
shell. However, the fluid conduits in the coupling
base of the instan~ invention enable transfer of
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1 heat away from the bearing area without the use of
heavy, bulky metallic heat absorbing structure.
Brief Description of ~he Drawings
Figure 1 is a perspective view of a motor
lamination and also a fragmentary, side view of a
plurality of windings for the motor of the instant
invention, as is seen before the laminations are
assembled to the windings;
Fig. 2 is a side fragmentary view after
assembly of the windings into the laminations;
Fig. 3 is a reduced, side cross-sectional
view of the next step of assembly wherein a stator
liner is inserted within the lamination stack, the
liner is expanded radially outward to contact the
interior edges of the laminations, and the ends of
the liner are thereaf~er outwardly swaged to form an
expanded, S-shaped configuration;
Fig.` 4 is a view depicting the next stage
of assembly~wherein 0-rings are mounted internally
and externally of the S-shaped portions on the
stator liner for engagement with recesses in a
coupling base and an end ring;
Fig. 5 is an illustration of the next step
of manufacture wherein the laminations are held in
compression between cylindrical projections on the
end ring and the coupling base;
- Fig. 6 depicts the next step of assembly
of the motor of the instant invention wherein the
coupling base, laminations and end ring are pressed
into an outer cylindrical shell, ~nd the laminations
are held in compression by the end ring and the
coupling base while the sheLl is formed to grip-
pingly engage the base and the ring;
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Fig. 7 is a cross-sectional view similar
to Fig. 6 wherein interior voids in the vicinity o~
the laminations and windings are filled with a
synthetic resinous adhesive;
Fig. 8 is an illustration depicting the
next step of assembly wherein the end faces, the
sleeve bearing and the bearing housing bore are
machined for concentricity and parallelism, and
thereafter the armature, the lower bearing and
bearing housing, and the end plate assembly are
installed in the motor, and finally pump staging is
brought into engagement with the coupling base and
pump casing is formed to complementally engage an
upper shoulder on the base; and
Fig. 9 is an enlarged, sectional view
taken along a portion of the line 9-9 in Fig. 7,
showing the bearing, the bearing support structure,
- and the fluid conduits within the support structure
for passage of coolant therethrough.
Detailed Description of the Drawings
The assembled submersible pump 20 of this
instant invention, as best seen in Fig. 8, includes
an electric motor assembly 22 as well as a pump
assembly 24. The motor assembly 22, in turn, in-
cludes a plurality of windings 26 (see ~'igs. 1-2)
that are inserted within notches 28 of a stack 30 of
a plurality of generaIly flat, ringlike laminations
32, the stack 30 comprising a field magnet for the
motor assembly 22.
As best seen in Figs. 4-6, an end ring 34
is disposed adjacent a first end 36 of the stack 30,
and a coupling base 38 is disposed adjacent a second
end 40 of the stack 30. A tubular, generally cylin~
drical outer motor shell 42, preferably comprised of
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stainless steel, surrounds the stack 30 and is
secured to the end ring 34 and the base 38. The
shell 42 has an inner diameter equival.ent to or
slightly smaller than the diameter of the cylin-
drical outer edge of. each of the laminations 32,
such that the shell 42 directly engages the outer
edge of the laminations 32 to substantially preclude
shifting of the latter in a transverse direction
relative to the stack 30. The shell 42, being
electrically conductive, thereby provides a con-
tinuous grounding structure for the motor assembly
22.
The base 38 is comprised of a generally
cylindrical body portion 44 having structure or.a
cylindrical projection 46 for contacting the second
end 40 of the lamination stack 30. The projection
46 has an outer edge 48 which flatly engages the
- outer lamination face of the first stack end 360
The edge 48 is provided with recess means or a
plurality of scallops 50, .for purposes to be ex-
` plained hereinafter. ..
- The body portion 44 of the base 38 also
has a shoulder 52 that is parallel and coaxial with
the edge 48. The shoulder 52 is adapted for engage-
ment with an end por~ion of the shell 42 and for
supporting the latter in generally concentric align-
ment with the lamination stack 30 as well as the
body portion 44. Disposed intermediate the shoulder
52 and the edge 48 are a pair of grooves 54, 54 for
supporting a pair of 0-rings 56, 56 respectivel~J
. (see Figs. 6-8).
-The base 38 is also provided with a recess
or groove 58 for containing an end portion of a
stator l.iner 60. Referring to Figs. 7-8, the end
portion on the left-hand side of the liner 60 is
formed into a generally S-shaped configuration, and elasto-
meric sealing means or a pair of O-rings 62 are located in
opposite portions of the S-shaped line end portion. The
cylindrical groove 58 is concentric with the outer corner
of the shoulder 52 as well as the grooves 54, the cylindrical
projection 46, the edge 48, and a pair of outwardmost
cylindrical surfaces 63, 63. Thus the groove 58 is operable
to generally retain the liner 60 in concentric relation
with the shell 42 and the base 38.
The body portion 44 of the base 38, being comprised
of a synthetic resinous material, is molded to grippingly
engage a bearing sleeve 64, the latter of which is provided
with serrations (an outer edge of one of which is indicated
at 66 in Fig. 9) on its outer surface for retaining the
bearing 64 in a fixed position relative to the base 38.
Thus, it can be seen that use of the lamination contacting
structure or projection 46 enables the bearing 64 to be
maintained in parallelism with the laminations 32, as
well as in alignment with the shell 42 by means of the
shoulder 52.
- As best seen in Fig. 9, the body portion 44
- inwardly of the groove 58 is provided with generally T-
shaped walls 68 in cross-section, which transversely are
fixedly interconnected to the circumscribing serrations
(such as at 66) on such the bearing 64. Intermediate
the walls 68 are a plurality of fluid conduits 70, each
of which includes a relatively small, elongated passage-
way 72 communicating with the adjacent, serrated area
of the bearing 64 and also a relatively large, elongated
channel 74 in side-by-side, fluid communicating relation-
ship to the passageway 72. The fluid conduits 70 thus
enable the passage of coolant directly to the bearing
and consequently reduce the danger of excessive
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11
1 accumulation of thermal energy in the synthetic
resinous body portion 44 surrounding the bearing 64.
Referring now to Fig. 7 in particular, it
can be seen that the passageways 72 communicate in
an area to the left of the bearing 64 and also to an
area to the right of the bearing 64, the latter area
also in communication with four radially extending
ducts 76. The ducts 76 facilitate circulation of
water to an area between an armature 78 and the
stator liner 60 (see Fig. 8) which would otherwise
be substantially blocked by a phenolic washer 80
disposed between the bearing 64 and the armature 78.
The armature 78 includes a shaft 82 that
extends through the bearing 64 and to a coupling 84
which matingly interconnects the armature shaft 82
to a pump stage drive shaft 86. A generally U-
shaped wiping seal 87 surrounds the armature shaft82 within a recess of the base 38 for generally
excludlng the entry of sand and other contaminants
from the pump assembly 24 and into the area adjacent
- the bearing 64. ..
The base 38 has an outer edge 88, as
illustrated in Figs. 4-8, which comprises a means
for supporting pump staging 90 in substantial, axial
alignment with the laminations 32. Moreover, the
base 38 has a second shoulder 92 that is disposed
remote from the first shouLder 52. The shoulder 92
comprises means adapted for engagement with a com-
plementally formed end portion 94 of a tubular,
cylindrical pump casing 96. The shoulder 92 sup-
ports the casing 96 in axially aligned relationship
with the motor shell 42, the laminations 32, the
armature 78 as well as the staging 90. Adjacent the
shoulder 92 is a groove 98 to enhance suppor~ of the
casing 96. Moreover, the shoulder 92 and ~he edge
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. 12
88 cooperate to main tain the impeller (not shown) of
the staging 90 in concentric alignment with the
shafts 82, 86.
The base 38 additionally has a channel for
S receiving an electrical wire 100 (Fig. 8) and a
water resistant connector 102, the wire 100 being
coupled to the windings 26 for supplying power
thereto. A pair of tabs 104 extend outwardly from
the base 38 to releasably secure a wire guard (not
shown). Also, the base 38 is provided with a fluid
inlet 106 for the pump assembly 24, and the inlet
.i 106 has a plurality of strain ing bars 108. A slot
--- lll is disposed adjacent the inlet 106 for the
- ~ ejection of sand or other abrasive contaminants from
the area adj acen t the seal 87.
The end ring 34 is somewhat similar in
nature to ~che base 38. Tha~ is to say, the end ring
34 has a generally cylindrical body portion 110 with
a pair of outwardmost cylindrical surfaces 112, 122.
The body 11Q.also has an outer shoulder 114 compri-
:: sing a mean~. adapted for supporting one end of the
motor shell 42 in surrounding, concentric alignment
~~ with the liner 60. A pair of grooves ll6, 116
receive elastomeric sealing means or 0-rings 118,
118 for sealing engagement of the ring 34 to the
shell 42.
The body portion 110 of the ring 34 is
provided with a generall~ cylindrical proj ection 120
having an outer edge 122 for flatly engaging a
lamination face at the first end 36 of the stack 30.
Thus, the edge 122 is operable to support the ring
34 in parallel and concentric alignment with the
laminations 32 as well as the shell 42 and the liner
60. The edge 122 i~s provided with a plurality of
.
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l scallops 124 (see Figs. 4~6) similar in configura-
tion to the scallops 50 of the edge 48.
The end ring 34 has a recess 126, as best
illustrated in Figs. 7-8, for receiving an expanded,
generally S-shaped configured, right-hand end por-
tion of the stator liner 60. The S-shaped portion
receives an elastomeric sealing means or a pair of
O-rings 128, 128, the outer of which sealingly
engages the end ring 34 in the recess 126 for re-
sisting passage of water between the liner 60 and
the end ring 34.
The end ring 34 also has a bore 130 for
slidably receiving a bearing housing 132, a circum-
ferential portion of which engages the inner O-ring
128. A sleeve bearing 134 is pressed into a central
channel through the housing 132 and complementally
supports the right hand end of the armature shaft
82, as illustrated in Fig. 8. A pair of axially
extending channels (not shown) disposed in the
housing 132.adjacent the bearing 134 enables fluid
communication between the areas within the liner 60
and a check valve 136, the latter of which.permits
en~ry of fluid upon demand.
An end cap 138 mounted over the check
valve 136 is bolted to the end ring 34 for retaining
the bearing housing 132 securely in the bore 130.
Additionally, a thrust washer 140 is conventionally
disposed between the bearing housing 132 and an end
of the armature 78.
Moreover, the end ring 34 has an elongated
passage 142 to enable injection of a quantity of
synthetic resinous adhesive or epoxy 144. The epoxy
144 flows into voids around the windings 26 and the
laminations 32. A portion of the epoxy 144 also
flows into the areas adjacent the scallops 50, 124
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l such that the epoxy 144, after hardening, precludes
relative rotation of the base 38 and the end ring 34
respectively. As the motor assernbly 22 is filled
with the epoxy 144, a passage in the base 38 (not
shown) permits escape of air. Once a sufficient
quantity of epoxy 144 is injected, a brass pin 146
is pressed into the passage 142, and a second pin
(not shown) is pressed into the passage in the base
38.
lOIn the method of assembly of the submers-
ible pump 20, the laminations 32 are slidably in-
stalled over the windings 26 so that the latter are
disposed within the notches 28, as shown by the
arrows in Fig. 1. All of the laminations 32 thus
lS form the stack 30, as shown in Fig. 2.
Next, the stator liner 60 is inser~ed
within the core of the stack 30, and as the lami-
- nations 32 are compressed together, the liner 60 is~
expanded in a radially outward direction to bear
against the interior edges of the laminations 32, as
illustrated in Fig. 3. As sho~n, a portion of the
liner 60 extends outwardly in ~oth directions from
the windings 26, and this portion is then swaged to
form an expanded cylindrical area, a portion of
which has the aforementioned generally S-shaped
configuration.
Referring now to Fig. 4, the O-rings 62,
128 are next installed on each end of the liner 60
`in opposite portions of the S-shaped liner area.
The end ring 34 and the base 38 are then brought
into a position such that the edge 122 of the end
ring 34 engages a flat face of the first stack end
36, and the edge 48 of the base 38 engages the flat
face of the second s~tack end 40. At the same time,
the outwardly extending ends of the liner 60 are
slidably inserted within the groove 54 of the base
38 and the recess 126 of the end ring 34, such that
the 0-rings 62, 128, 62 sealingly engage the end
ring 34 and the base 38 respectively.
Next, with reference to Fig. 5, a force is
exerted on the base 38 and the end ring 34 such that
the laminations 32 are maintained in compressive
interengagement. Provision of the edges 48, 122
thus enable the cylindrical base 33 and -the end ring
34 to be held in alignrnent with the stack 30 as the
latter is compressed. The 0-rings 56, 56, 118, 118
are then installed on the base 38 and end ring 34q
Subsequently, the end ring 34, the base 38
and the stack 30 are pressed under pressure into che
tubular sheLl 42, the latter of which preferably has
a diameter slightly smaller than the outerwardmost
surfaces 63, 63 of the base 38, the surfaces 112,
- 112 of the end ring 34, and the outer surface of the
stack 30 to provide a slight interference fit. The
diameter of the base surfaces 63, 63 is substanti-
ally equal to the diameter of the surfaces 112, 112,
but advantageously they differ very slightly in
diameter for ease of forming. In one example, the
surfaces 63, 63 have a diameter of 3.604 to 3.610
inches, the surfaces 112, 1l2 have a diameter of
3.597 to 3.603 inches, the outer surface of the
lamina~ion stack 30 has a diameter of 3.602 to 3. 604
inches, while the shell 42, by comparison, has an
inner diameter of 3.589 to 3.597 inches before
assembly of the pump 20.
While the base 38 and the end ring 34 are
compressed against the stack 30, each end of the
shell 42 is then roll- formed to bend around the
shoulders 52, 114 as well as tightly engage the 0-
rings 56, 118. Thereafter, the formed ends of the
, :
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16
l shell 42 are thus operable to retain the base 38,
the end ring 34 and the stack 30 in compressed,
assembled relationship.
Next, viewing Fig. 7, a quantity of the
epoxy 144 is forced under pressure through the
passage 42 to fill voids around the windings 26 and
the laminations 32. Subsequently, the pin 146, as
well as a second pin for the air escape hole, is
pressed into the end ring 34 and the base 38 re-
spectively for sealing engagement therewith.
Then, the motor assembly 22 is gripped
around the exterior surface of the shell 42 and the
bore of the bearing 64 as well as the bore 130 in
the end ring 34 are machined for concentricity and
parallelism. At the same ti~e, the left hand edge
88 of the base 38, viewing Fig. 7, as well as the
right hand edge of the end ring 34 are faced in true
- orthogonal relationship to the bearing 64 and the
bore 130.
Subsequently, as shown in ~'ig. 8, the
armature 78 is installed such that the shaft 82
extends through the bearing 64 and thereafter the U-
shaped seal 87 is installed around the shaft 82.
The thrust washer 140 as well as the bearing housing
132 containing the bearing 134 are then installed at
the opposite end of the armature shaft 82. The
check valve assembly 136 is positioned over the
bearing housing 132,~and the end cap 138 is then
bolted onto the end ring 34 to secure the housing
132 in position.
Next, the coupling 84 is installed over
the shaft 82 and the drive shaft 86 along with the
staging 90 are brought into position such that the
outer edge of the staging 90 flatly engages the edge
~ ~ ~33 ~
88 of the base 38. The pump casing 96 is then
formed to grippingly engage the shoulder 92.
As should now be obvious to those skilled
in the art, the provision of the lamination engaging
structure or edges 48, 122 of the base 38 and the
end ring 34 respectively enables the stack 30 to
easily be maintained in alignment with the base 38
and the end ring 34 so that the bearings 64, 134 are
also maintained in alignment with the lamination
stack 30. Thus, manufacture of the motor assembly
22 is simplified over prior art motors having end
rings welded to the stator liner and an outer shell,
since such rings must be held in alignment during
welding and the position of the lamination stack
within the liner and the shell cannot be precisely
controlled~
Moreover, direct compression of the lami-
~ nations 32 in the instant invention between the base
38 and the end ring 34 eliminates the necessity for
utilization of cleating or straps to hold the lami-
nations 32 together during assembly. Elimination ofsuch cleating reduces costs and also eliminates an
extra step during assembly.
Moreover, by utilization of a press fit
between the shell 42 and the laminations 32, the
shell 42 is thus operable to substantially preclude
shifting o~ the laminations 32 in a transverse
direction relative to the stack 30. By comparison,
prior art motors were generally dependent on either
the cleating or the epoxy adjacent the laminations
in an attempt to preclude shifting of the latter.
Machining of the motor assembly 22 for
precise orientation of the armature 78 of the in-
stant invention is also simpli~ied in comparison to
prior practice. By provision of a base 38 directly
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18
securing the bearing 64, the use oi a bearing hous-
ing supported by the base 38 is rendered unneces-
sary, thereby reducing the buildup of tolerance
limits of the assembly accordingly. At the same
time, as the edge 88 is faced, the edge 88 can be
brought into true perpendicular relationship to the
bore of the bearing 64 so that the staging gO, as
well as the casing 96, are in alignment with the
bore of the bearing 64.
Because the base 38 and the end ring 34
are comprised of an electrically insulative syn-
thetic resinous material, the windings 26 can engage
the base 28 and the end ring 34 in pressing contact
therewith without fear of damaging the insulation on
lS the windings 26 and thereby creating a ground fault
path. Thus, during assembly, the ends of the wind-
ings 26 of the instant invention can be significant-
ly compressed such that the overall length of the
motor assembly 22 is reduced. By comparison, cer-
tain prior art motors used teflon tape or other
extra, insulative material at the end of the windingloops and adjacent the metallic end structures in an
effort to reduce the possibility of such ground
faults.
