Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention relates to a composite
cynamoelectric machine, and more particularly to the brush
arrangement of a composite dynamoelectric machine comprised
of two or more DC axial air-gap machines joined by a common
shaft.
Axial air-gap machines, sometimes referred to as
disc machines, have the characteristic, distinct from radial
; air-gap machines, of being much shorter in their axial
dimension, for a given power rating. In many instances
this means that the axial air-gap machine can be mounted
directly onto the equipment with which it is being used,
resulting in a quite compact overall arrangement; at least more
compact than that which would result from the use of a
radial air-gap machine.
In some cases, such as for example with a disc
motor connected to drive a load, the motor may not have
sufficient power. Drawing from the field of radial air-gap
motors, obvious solutions to such a problem are either to
; use a motor with a higher power rating, or to use two
2Q motors to drive the same load.
Disc motors having permanent magnet rotors lend
themselves quite nicely to the solution of employing two
(or more) motors to drive the load. As disc motors are
relatively short in their axial direction, two disc motors
can be arranged on a common shaft, retaining the same radial
dimensions as a single motor, and having an axial length
that is not normally objectionable since it is only approxi-
mately twice the short axial length of a single disc motor.
` Such an arrangement consists, in simplistic terms, of
3~ mechanically connecting the two motors together, and is
not normally a complicated matter.
However, in the case of a wound disc rotor (such
as in a DC motor) where electric current must be conducted to
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the rotor by brushes, the solution is not quite so simple.
Normal brush arrangements on DC disc motors either do not
allow for a mounting of the motors that is sufficiently
close in the axial direction as would be desirable for a
compact assembly, or else, if a compact assembly is obtained,
it does not allow for easy servicing of the brushes, and
the resulting assembly has to be dismantled to allow the
brushes to be changed or inspected. Since changing brushes
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is a common and regular aspect of DC motor maintenance,
this presents a serious problem if a compact assembly of DC
disc motors is desired.
The present invention eliminates many of the
problems associated with the brushes of a DC disc motor
in such a compact assembly in the following manner. The
rotor is provided with its commutator near its radial
periphery and the brushes ~and their associated assemblies~ --
are consequently located near the outer periphery of the
stator. The brushes, rather than being aligned with their
longitudinal axes parallel to the longitudinal axis of
the shaft, have their axes inclined at an angle therefrom.
This angle can perhaps best be described as a compound
; angle comprised of a first angle, in a radial direction, away
~` from the longitudinal axis of the shaft, and a second angle,
in a direction perpendicular to the direction of the first
angle (i.e. a generally circumferential direction, as opposed
ko a radial direction), with all brushes on the same side
inclined alike. The result of such brush positioning is
;~ that the two or more DC disc motors can be mounted together,
on a common shaft, with the stator of one motor touching the
stator of another motor, and yet the brushes remain readily
accessible so that the brushes can be removed and replaced
wikh the com~ination of DC disc motors remaining intact.
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., In another way, the present inventi.on can be
described as a composite dynamoelectric machine comprising
- two or more axial air-gap machines joined by a common shaft;
. each of the axial air-gap machines is characterized by
~ brush.es located near th.e outer radial perlphery o~ the
~ axial air~gap machine, on at least one axial side, and
inclined such th.at the outer extremities of the brushes are
further removed from the shaft than are the inner extremities
of the brushes.
:~. lQ In yet another way, the present invention can be
described as a composite dynamoelectric machine comprising:
at least two axial air-gap motors joined by a common shaft;
. each axial air-gap motor has brushes located on both axial
. sides, near the outer radial periphery; each brush protrudes
~ from an axial side of a motor at the same compound angle;
: the compound angle comprised of à~ a radial angle between
the plane of the commutator surface and the axis of the
- brush, the radial angle being greater than zero degrees and
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less than 8a degrees, and b~ a circumferential angle, between
2~ the axis of the brush and th.e plane of the commutator, the
circumferential angle being greater than zero degrees and
less than 80 degrees; the compound angle being of a magni.tude
that the brush.es of the at lea~t two motors do not interfere
; with one another when th.e motors are combined to form th.e
. composite dynamoelectric machine.
.. The invention will now be described in more detail
w.ith reference to the accompanying drawings, wh.erein like
parts in each of the several figures are identified by the
same reference character, and wherein:
;- 3Q Figure 1 is a partial sectional view of two disc
. motors incorporating the present invention;
::. Figure 2 is a partial sectional view of two disc
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motors connected to a load and incorporating the present
. invention;
Figure 3A is a perspective view of a rotor showing
.-~ its commutator segments and a reference co-ordinate system
.- for describing the orientation of the brushes;
;. Figure 3B depicts a typical brush in relation to
the co-ordinate system described in Figure 3A; -
Figure 4 depicts a variation of the embodiment
of Figure 2.
. 10 Referring now to Figure 1, there is depicted
therein two DC disc motors 10 and 11 constructed according to
.~ the present invention with their stators mechanically
:~ connected to one another by suitable known means; for
example, by bolts (.not shown). Motor 10 is identical
to motor 11; the way they are arranged in the drawings,
.~ one is the mirron image of the other. Since motors 10 and
. 11 are identical they wi.ll be described simultaneously with
li~e numerals being used to describe like parts in each motor.
Each motor 10 and 11 comprises a rotor 12 ~hich i5 mounted
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to a single shaft 13 that is common to both.motors 10 and 11.
Each rotor 12 is comprised of a hub portion 14 and an
-l electrical winding portion 15 secured to the hub portion
14. One type of winding suitable for the invention is
~` described in Canadian Patent No. 990,773 to E. Whiteley,
issued June 8, 1976. The winding comprises a number of
coils bonded together or cast in a resinous material, for
~ example, an epoxy resin to provide a rigid discoidal rotor.
; An annular array of commutator segments 16 are provided on
each side of the winding portion 15, adjacent the periphery
,. 3~ thereof, as shown, and these segments 16 form part of the
,. unitary structure. A band 17 of reinforcing material is
` bonded to the periphery of rotor 12. The band 17 is conveniently
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of la~ers of tape having glass fibers extending around the
peripher~ and bonded thereto.
A stator 18 has two generally disc-like housing
members 19 and 20 which include respectively covers 21 and
22 for the brush gear. The two housing members 19 and 2Q
are fastened together by bolts 23 and the members 20 include
bearings 34 to provide for rotation of the shaft 13 within
the stators 13. The brush mounted in housing member 21 can
be seen in motor 10 and is referenced by the numeral 24.
The brush mounted in housing member 22 can be seen in motor
11 and is referenced by t~e numeral 25. Mounting members 26
and 27, preferably of mild steel, are secured or fastened
to housing members 19 and 20 respectively. Permanent magnets
28 and 29 are mounted opposite one another to mounting
members 26 and 27. The permanent magnets 28 and 29
form the poles of the machine and any number of magnets
can be used for each pole. The motor field extends between
the poles; that is, it extends between magnets 28 and 29
~of the same motor), and through winding 15 of that
same motor. It will be seen that the field is su~stantially
parallel to the axis of shaft 13 and thus the motors 10 and
11 are axial air-gap motors. The mounting members 26 and 27
provide a magnetic path for the magnetic field circuit.
As is readily apparent from Figure 1, brushes 24
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`~ and 25 are inclined away from the shaft 13 (in a radial
direction) so that the outer extremities of the brushes 24
and 25 are farther from shaft 13 than are their inner
extremities which contact commutator segments 16. The
brushes 24 and 25 are also inclined in a second direction
(a circumfer4ntial direction) which is more clearly illustrated
`; in Figures 3A and 3B; in E'igure 1, however, it should be
` noted that ~rush 25 of motor 11 is inclined toward the viewer
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and brush 24 (enclosed by cover 21) of motor 11 is inclined
away from the viewer. Since motor 10 is identical to motor
11, but is situated in Figure 1 so as to be the mirror image
of motor 11, brush 24 of motor 10 is inclined toward the
viewer and brush 25 (enclosed by cover 22) of motor 10 is
inclined awa~ from the viewer. It should be noted that
brushes 24 and 25 are only two of several such devices
located around the peripheries of the stators 18 of the
motors 10 and 11. All the brushes 24 located on one side
of the stator 18 are all inclined alike; and all the brushes
25 on the other side of the stator 18 are all inclined
alike.
The inclination of the brushes 24 and 25 can
also be described in a somewhat more exacting manner, with
reference to Figures 3A and 3B, as follows. Figure 3A
depicts, in simplified form, the rotor 12 of one of the motors
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lQ, 11 and the shaft 13. Shown on the rotor 12 are the
commutator segments 16. A co-ordinate system is shown in
connection with one of the commutator segments 16. One
2Q point, approximately the centre o~ the exterior surface
of one commutator segment 16, is chosen as the origin 0
for the co-ordina-te system. The plane C-0-D is the plane
of the commutator surface, where the line 0-D is a radius
from the shaft 13 and the line 0-C is an arc with its centre
of curvature at shaft 13. The line 0-A is a perpendicular
to the plane of the commutator surface (i.e. perpendicular
, to khe plane C-0-D) and is parallel to the longitudinal axis
of shaft 13. The line 0-B represents the longitudinal
axis of a brush 24, 25. The line 0-CC is a tangent to the
line 0-C at the origin 0, in the plane C-0-D, such that
the lines 0-CC, 0-D, and 0-A now form an orthogonal
co-ordinate system. As a consequence, the planes A-0-D,
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A-~CC, and D-0-CC are all mutually orthogonal to one another.
Now, referring to E'iguxe 3s, a representative
brush 24 is shown superposed upon the orthogonal co-ordinate
system described above, with reference to Figure 3A. Brush
24 has a longitudinal axis 39 which passes through the origin
0 and is also referenced as line s-o. It can be seen from
Figure 3B that when the brush axis B-0 is referred to the
aforementioned planes, there will be a corresponding
projection of the brush axis on both plane A-0-CC, and plane
lQ A-0-D. These projected images of the brush axis B-0 on
the planes define the angles ~ and ~ as shown in Figure 3B.
The direction 0 to D is described as being the "radial"
direction and consequently angle ~ is referred to as the
radial angle between the brush axis 0-s and the commutator
plane D-0-CC. '~he direction 0 to CC is described as being
the "circumferential" direction and consequently angle
is referred to as the circumferential angle between the
brush axis 0-B and the commutator plane D-0-CC.
` While, from a theoretical point of view, the
angles ~ and ~ can range from zero to 90 degrees, it has been
found that an upper limit of 80 degrees for angle 0 is a more
practical limit (to ensure stability in the contact between
~; brush and commutator). The practical limits on angle g will
depend partly on the exact design of the machines, but the
upper limit will have to be less than 90 degrees in order
to provide e~sy access to the ~rushes in the completed
composite dynamoelectric machine. The lower practical
limit for both angles ~ and 0 will be greater than zero
degrees. The circumferential angle 0 is preferably between
65 and 75 degrees; the radial angle ~ is preferably approxi-
mately 60 degrees.
The result of such a construction can be seen
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at the juxtaposition of motors 10 and 11 near the brush
covers 21 (in Figure 1). It can be seen that brush 24 (of
motor 10) is inclined both away from shaft 13 and towards
the viewer. In contrast, brush 24 (enclosed in cover 21) of
motor 11 is inclined both away from shaft 13 and away from
the viewer. This enables housing members 19 of motors
10 and 11 to come into touching contact with one another
without any interference from the brushes 24 of the two
motors. At the same time, all brushes 24 are maintained
readily accessible from exterior both motors 10 and 11
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; without dismantling of the motors 10 and 11.
Figure 2 depicts two motors 30 and 31 that are
l very similar to motors 10 and 11 of Figure 1. The primary
i difference between the motors of the two Figures is that
,r~ motors 30 and 31 of Figure 2 do not have any bearings of
their own. The load 32 has an "overhung" shaft 33 supported
l by bearings 35 (of which only one is shown in the Fig.~.
i The stator of motor 30 is attached by mechanical means such
'`~ as bolts (not shown) directly to the frame of load 32 and
the rotors 12 of motors 30 and 31 are attached directly to the
shaft 33 of the load 32. In such an arrangement, separate
~ bearings for motors 30 and 31 are not required and hence can
`~¦ be eliminated. Additionally, a plate 36 is used to seal the
;~ opening in housing member 20 to prevent any contaminants from
i entering the motors 30 and 3I.
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; Figure 4 depicts a further variation of the
embodiment of Figure 2. In Figure 4 it is readily apparent
that the load 32 has a somewhat longer overhung shaft 38 and
, a ~earing 37 has been included in hous-ing member 2~ of the
outermost motor (i.e. motor 31~ to provide additional support
for the shaft. The decision of which embodiment (depicted in
~;, Figures 1, 2 and 4) to emplo~ will depend upon the specific
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application and it is not deemed necessary to comment upon
the criterion involved in such a decision, as it is beyond
. the scope of the present specification.
Obvious variations to this invention would include
ma]cing housing member 19 identical to housing member 20.
This would result in a standardization of components for the
:: motor combination, and the embodiment of Figure 1 would be
, realized by using bearings 34 only in combination with
., the outer housing members of the motor combination, and not
lQ with the inner housing members. This variation is also
equally applicable to the embodiments of Figures 2 and 4.
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