Improved Commutator for Dynamo Electric Generators and Motors.
Year: 1890

page_text: Date of Application, 12th Nov., 1890
Complete Specification Left, 8th Sept., 1891-Accepted, 10th Oct., 1891
PROVISIONAL SPECIFICATION.
Improved Commutator for Dynamo Electric Generators and Motors.
We, HENRY DAVIS, Electrical Engineer, of All Saints Works, Derby, in the
County of Derby, and ARTHUR HENRY STOKES, one of Her Majesty's Inspectors
of Mines, of Green Hill, Derby, in the County of Derby, do hereby declare the
nature of this invention to be as follows:-
The object of this invention is to so construct the commutator of dynamo electric
generators and motors that the surrounding atmosphere shall be so excluded from
the commutator bars and the brushes, that when working in a gas impregnated
atmosphere all chance of the surrounding gas impregnated atmosphere becoming
ignited by sparking at the commutator will be avoided, while such commutator
and brushes will be efficiently protected from the damaging and disturbing effects
of weather, dust, etc.
The invention consists broadly in reversing the usual construction of commu-
tators by arranging the commutator bars in the form of a cylindrical ring and
arranging the brushes within such cylindrical ring and causing them to bear upon
the inner surface thereof.
A suitable method of carrying the invention into effect consists in clamping the
commutator bars between rings to bear on the ends of the bars, such rings being
connected together by tie bars. The commutator bars are insulated from each
other and from the rings.
The inner clamping ring is attached to a circular plate which screws on to the
commutator shaft, while an end plate screws on to the outer ring and has a central
opening through which a sleeve cylinder carrying the brushes projects to the inside
of the commutator ring. This end plate is preferably provided with openings in
which horn, glass or other transparent material is inserted, so as to form windows
for enabling the commutator and brushes to be inspected during working, while
preventing the admission of gases or dust.
The sleeve cylinder carrying the brushes surrounds the commutator shaft with
which it forms a loose but nearly tight fitting joint at its ends, and the part outside
the commutator ring is provided with a flange which also forms a loose but nearly
tight fitting joint against the outer surface of the end plate round the opening
therein through which such sleeve cylinder projects to the inside of the commutator
ring.
The brush holders are carried by and insulated from the sleeve cylinder, the
latter being pierced with a hole or holes from the brushes to the outside of the
commutator ring for the passage of the leads to the brushes. The brushes carried
in the holders are forced outwards by springs so as to bear against the inner
surface of the cylindrical ring formed by the commutator bars.
The sleeve cylinder carrying the brush holders has arms projecting from its
outer end, such arms serving to regulate the lead of the brushes by adjusting the
ends of such arms within brackets which they engage (thereby shifting the sleeve
cylinder round the shaft), and then by means of clamping screws securing such
arms in the position to which they have been adjusted.
By unscrewing the end plate from the outer clamping ring and releasing the
ends of the arms of the sleeve cylinder from the brackets they engage, the sleeve
cylinder can be slid along the shaft, thus drawing out the brushes from the inside
of the commutator ring when required for cleaning or repairing the same, a
sufficient space being left between the end plate and the end bearing to enable this
to be effected

page_text: If required, binding wires insulated from the commutator bars may be wound
outside the ring of such bars so as to give greater stability to such ring.
Dated this 12th day of November 1890.
ALLISON BROS.,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improved Commutator for Dynamo Electric Generators and Motors.
We, HENRY DAVIS, Electrical Engineer, of All Saints Works, Derby, in the
County of Derby, and ARTHUR HENRY STOKES, one of Her Majesty's Inspectors
of Mines, of Green Hill, Derby, in the County of Derby, do hereby declare the
nature of this invention and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement :-
The object of this invention is to so construct the commutator of dynamo electric
generators and motors that the surrounding atmosphere shall be so excluded from
the commutator bars and the brushes, that when working in a gas impregnated
atmosphere all chance of the surrounding gas impregnated atmosphere becoming
ignited by sparking at the commutator will be avoided, while such commutator
and brushes will be efficiently protected from the damaging and disturbing effects
of weather, dust, etc.
In carrying out this invention we reverse the ordinary construction of commu-
tators by arranging the commutator bars in the form of a cylindrical ring and
arranging the brushes within such cylindrical ring and causing them to bear upon
the inner surface thereof.
In the accompanying drawings
Fig. 1 is partly a side elevation and partly a longitudinal section of a commu-
tator showing one method of carrying our invention into effect, and
Fig. 2 an end view thereof showing suitable means for adjusting the lead of the
brushes.
Fig. 3 is a longitudinal section of a commutator showing a slightly modified
method of carrying our invention into effect, and
Fig. 4 is an end view of Fig. 3 showing the means employed for clamping the
brushes and of varying the pressure of same on the commutator from the outside
while the machine is running.
Fig. 5 is an end view of a slightly modified form of the means or clamping the
brushes and varying the pressure of same on the commutator, and
Fig. 5 is a side elevation of Fig. 5.
The method of carrying the invention into effect shown in Figs. 1 and 2 consists
in clamping the commutator bars A between rings C, D, which bear on the
ends of the bars, such rings being connected together by tie bars B. The com-
mutator bars A are insulated from each other and from the rings C, D.
The inner clamping ring C is attached to or forms part of a circular plate C
which screws on to the commutator shaft M, while an end plate E screws on
to the outer ring D and has a central opening through which a sleeve cylinder K
carrying the brushes G projects to the inside of the commutator ring. This end
plate E is preferably provided with openings F in which horn, glass or other
transparent material is inserted, so as to form windows for enabling the com-
mutator and brushes to be inspected during working, while preventing the admission
of gases or dust.
The sleeve cylinder K carrying the brushes G surrounds the commutator
shaft M with which it forms a loose but nearly tight fitting joint at its ends,
and the part outside the commutator ring is provided with a flange k which also
forms a loose but nearly tight fitting joint against the outer surface of the end
plate E round the opening therein through which such sleeve cylinder projects to
the inside of the commutator ring.

page_text: The brush holders J are carried by and insulated from the sleeve cylinder K,
the latter being pierced with a hole or holes L from the brushes to the outside of
the commutator ring for the passage of the leads to the brushes. The brushes G
carried in the holders J are forced outwards by springs R so as to bear against the
inner surface of the cylindrical ring formed by the commutator bars A, a pin
and slot connection S serving to guide the brushes in such movement.
The sleeve cylinder K carrying the brush holders J has arms O projecting from
its outer end, such arms serving to regulate the lead of the brushes by adjusting
the ends of such arms within brackets P which they engage (thereby shifting the
sleeve cylinder round the shaft), and then by means of clamping screws N securing
such arms in the position to which they have been adjusted.
By unscrewing the end plate E from the outer clamping ring D and releasing
the ends of the arms O of the sleeve cylinder K from the brackets P' they engage,
the sleeve cylinder K can be slid along the shaft, thus drawing out the brushes (
from the inside of the commutator ring when required for cleaning or repairing
the same, a sufficient space being left between the end plate E and the end
bearing Q of the commutator shaft M to enable this to be effected.
As the end plate E is secured to the ring D of the commutator and revolves
with it, and the brushes cannot be removed until the plate E is unfastened from
such ring, it will be seen that this cannot be effected while the machine is
running and further, it will be seen that the plate E must be again secured
to the ring D before the machine can be again run. It, therefore, follows that
the commutator and brushes cannot be exposed or opened to the atmosphere
while the motor is running, and all chance of an explosion occurring is conse-
quently avoided.
If required, binding wires or strips V insulated from the commutator bars A.
may be wound outside the ring of such bars so as to give greater stability to such
ring.
In the arrangement shown in Figs. 3 and 4 the inner clamping ring C¹ is
screwed or keyed on to the shaft M thus forming a permanently closed end to
the commutator cylinder. The commutator bars or segments A are clamped
between this plate C¹ and the ring D, by studs or bolts B, insulated from the bars
or segments A.
The commutator bars or segments A are in the form of a T, the stem of which
is brought outside the cylinder in order to make the connection to the armature
coil. The under side of the top of the T is slightly bevilled the plate C¹ and the
ring D being also bevilled to a corresponding degree so that the segments will be
drawn together when the ring D is clamped to the plate C, the space X being
left for that purpose.
The commutator bars or segments are insulated from each other and the
surrounding metal by vulcanized fibre or other suitable insulating material, the
insulation being represented by thick black lines.
The face of the commutator cylinder is closed by a locking ring E and a disc E',
the latter carrying the brush holders J and having windows formed therein.
As will be seen the disc El consists of two rings, the inner one, which slides on the
extended shaft bearing or sleeve K and carries the brush holders J, and the outer
one, which is rivetted to the inner; the windows F being held between the two.
This disc E' in connection with the locking ring E makes the dust and flame
tight joint as shown. A raised edge on the locking ring E serves to lock the head
of every bolt B used for clamping the commutator bars or segments, thus preventing
any bolt or segment becoming loose whilst revolving.
The locking ring E screws or joints on to a projecting piece on the ring E'.
This locking ring is so made that the rotation of the machine tends to tighten it,
thus in a machine running clockwise (viewed from the commutator end) the thread
on the locking ring is left handed, and in a machine running counter clockwise the
thread is right handed.
The bearing or sleeve K is elongated into the commutator cylinder, the disc E'

page_text: as above stated sliding on it. This arrangement also protects the bearing from
grit or dust.
The arm J
insulated from it.
of the brush holder passes loose tight through the disc E', but is
In the arrangement shown in Fig. 4 for clamping the brushes and for varying
the pressure of such brushes on the commutator from the outside, whilst the
machine is running, the clamping handles Y, Y, are attached to the disc E¹,
screwing through lugs cast on the disc and pressing on to the extended bearing or
sleeve K. This arrangement is to allow of the lead of the brushes being adjusted
whilst the machine is running. By slackening the handles Y, Y, the disc E' will
be free to revolve, (it being prevented from opening the cylinder by the locking
ring E). When the proper adjustment is obtained the disc E' (and therefore the
brushes) is clamped (to the extended bearing or sleeve K) in position by screwing
up the handles Y, Y.
To the outside end of each of the brush holder arms J', is attached a lever Z, to
the end of which is attached a spring Z, the tension of which can be increased or
diminished by tightening or loosening the milled nut 22. The position of the
brushes is indicated in dotted lines. To increase the pressure of the brushes on
the commutator, it is only necessary to increase the tension of the spring Z', by
tightening the milled head Z².
The brush connections W are made from the levers Z.
The edge of the locking ring E is preferably notched in order to facilitate the
screwing of it up.
To open the commutator for cleaning etc., the locking ring E is unscrewed, the
handles Y, Y, are loosened and the disc E' and the parts attached thereto slide out
towards the bearing Q.,
In the arrangement shown in Figs. 5 and 6 the locking ring E and disc E are
combined in one, and in this case one handle Y only is employed, acting in the
same manner as in the arrangement shown in Figs. 3 and 4.
To the upper brush arm Jis attached a double lever Z, and to the lower brush
arm is attached a single lever Z. The right hand end of the upper lever Zis
connected to the right hand end of the lower lever Z by a bar K¹ of
vulcanized fibre, or other suitable insulator. To the left hand end of the double
lever is attached one end of a spring Z', the other end of which is attached to a
milled head nut Z, working against a lug cast on the ring E. The arrangement
is operated in the same way as in the previous arrangement, but in this case,
however, the pressure on both brushes is increased or diminished at the same time
and to an equal amount on each brush, whereas in the previous case the pressure of
one brush is varied independently of that of the other.
The connections W are made to the levers Z in this case beneath screws.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is
-
1. The improved commutator consisting of a set of insulated commutator bars or
segments arranged in the form of a cylindrical ring clamped between an inner ring
secured to the commutator shaft, and an outer ring tied or bolted to such inner
ring, while a locking ring is screwed on to or otherwise detachably secured to the
outer ring and has an opening through it for the passage of the part carrying the
commutator brushes, so that the latter can bear on the inside of the ring of com-
mutator bars or segments, while the joint between the locking ring and the part
carrying the brushes is of a loose tight nature, so as to produce a dust and flame
tight joint without the use of packing, substantially as described and shown.
2. The improved commutator consisting of a set of insulated commutator bars or
segments arranged in the form of a cylindrical ring closed at both ends, and o
brushes bearing against the inner surface of such ring and carried by a sleeve
projecting through an opening in the plate closing the outer end of the ring, such

page_text: sleeve passing through the outer plate so that it can be turned in relation thereto
and yet form a flame tight and dust tight joint at the opening through which it
passes without the use of packing, substantially as herein described and shown
in Fig. 1 of the drawings.
3. The improved commutator consisting of a set of insulated commutator bars or
segments arranged in the form of a cylindrical ring clamped between an inner ring
secured to the commutator shaft and an outer ring tied or bolted to such inner ring,
to which a locking ring is screwed or otherwise detachably secured, such locking
ring fitting over a sliding disc to which brush carriers projecting within the ring of
commutator bars or segments are secured, the joint between the locking ring and
such disc being of a loose tight nature, so as to produce a dust and Hame tight
joint without the use of packing, substantially as described and shown in Fig. 3 of
the drawings.
4. The combination with the ring of commutator bars or segments A and the
sleeve K carrying brushes G bearing on the inner surface of such ring, of arms O,
projecting from such sleeve K outside the ring of commutator bars or segments and
engaging brackets P, their positions in such brackets being adjustable so as to
regulate the lead of the brushes, substantially as herein described and shown
in Figs. 1 and 2 of the drawings.
5. The improved arrangement for clamping the brushes of commutators which
consist of a set of insulated commutator bars or segments in the form of a ring
closed at each end, and on the inner surface of which ring of bars or segments the
brushes bear, and also for varying or regulating the pressure of such brushes on
the commutator bars or segments from the outside while the machine is running,
such arrangement being constructed and operating substantially in the manner
herein described and shown in Fig. 4 of the drawings.
6. The improved arrangement for clamping the brushes of commutators which
consist of a set of insulated commutator bars or segments in the form of a ring
closed at each end, and on the inner surface of which ring of bars or segments the
brushes bear, and also for varying or regulating the pressure of such brushes on
the commutator bars or segments from the outside while the machine is running,
such arrangement being constructed and operating substantially in the manner
herein described and shown in Figs. 5 and 6 of the drawings.
Dated this 28th day of August 1891.
ALLISON BROS.,
Agents for the Applicants.