Improvements in Commutators for Dynamo-electric Machines.
Year: 1890

page_text: Date of Application, 5th Aug., 1890-Accepted, 11th Oct., 1890
COMPLETE SPECIFICATION.
Improvements in Commutators for Dynamo-electric Machines.
I JAMES WATSON EASTON of 45 Broadway in the City, County and State of New
York, United States of America Electrician 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:-
It
My invention relates to dynamo-electric machines and motors, and it consists in a
novel form, construction and arrangement of the sections of the commutator.
consists further in the provision of means for preventing short circuiting between the
sections of my improved commutator, and it consists further in the novel construction,
arrangement and combination of parts hereinafter more specifically described and
claimed.
In dynamo electric machines the requisite pressure of the brushes against the
commutator cylinder produces sufficient friction to soon wear away the surface of the
commutator, and in such machines, as heretofore constructed a channel is speedily.
formed around the periphery of the commutator where the brushes come in contact
with it. The sides of this channel are not straight and true but are rounded or
bevelled owing to the vibration of the shaft of the machine and also to the variation'in
the position of the brushes. The bottom of the channel also becomes uneven, and in
consequence the contact between the brushes and the commutator will be very intimate
at some points in the width of the brushes while at others they will not be in contact
at all. This causes an excessive amount of sparking and such a variation in the
operation of the machine that the operation of the apparatus connected with it is often
seriously interfered with.
The object of my invention is to prevent the uneven wearing away of the commu-
tator sections and to afford an even bearing for the extremities of the brushes until the
commutator is entirely worn out.
In the accompanying drawings
Figure 1 is a longitudinal sectional view of a commutator constructed in accordance
with my invention.
Figure 2 is an end elevation partly in section on the line 2-2 (Figure 1).
Figure 3 is a view in elevation of one of the sections of iny improved com-
mutator, and
Figure 4 is a corresponding view of one of the sections of a commutator of the
ordinary construction showing the groove worn therein by the brushes of the machine.
Similar letters of reference are used to indicate corresponding parts in all the
views.
A
The sleeve or hub A is adapted to be suitably secured to the shaft of the machine
and serves to support the commutator sections B in any usual manner.
As shown the
inner end of the sleeve A is provided with the undercut flange a and the other end of
the sleeve is screw-threaded to receive the nut C which bears against the undercut
collar 1) which is adapted to slide along the sleeve A. The commutator. sections are
suitably insulated from the sleeve and collar, and also froin each other by strips or
rings of insulating material E. When the commutator sections are placed in position
the nut C is screwed up tightly against the collar D, which in turn exerts sufficient
pressure against the sections to hold them firmly in place.
The commutator sections B consist preferably of thin sections-of-copper and are
preferably provided with the projecting arm b for the attachment of the armatüre
coils. They are advantageously made considerably deeper than is ordinarily done so
that they will project out beyond the outer surface of the collar D. Each of the
sections B is provided with a slot 6' at a distance from the outer edge of the section

page_text: equal to the width of the brushes to be used. When the sections are in position, these
slots form a continuous channel around the periphery of the commutator, and the
depth of the slots is such that the channel will extend down to the point to which
the sections can be worn before being discarded. These slots may be formed in the
sections in any desirable way. For instance, they may be formed separately before
the sections are mounted on the shaft, or they may be cut simultaneously after these
sections are in position, care being taken that the edges of the channel are even and
preferably at right angles to the axis of revolution. As thus constructed an even
wearing or contact surface is provided for the commutator of the exact width of the
brushes, and this surface is evenly maintained until the sections are worn down
to the depth of the channel or groove, when the sections may be. replaced by
new ones.
I
In order to prevent the possibility of the short circuiting of the commutator which
might ensue if the groove were to become filled with dust, dirt and abraded metal, I
fill the groove with any suitable insulating material 62, preferably such as can be readily
removed in layers as the contact, surface of the commutator is worn away.
prefer to fill the groove in the following manner, although it is to be understood that
I do not limit myself thereto. A layer of varnish or glue is first put into the bottom
of the groove and then a layer of flax, thread such as is used by harness or shoe-
makers, is wound therein. This is then coated with the varnish, or glue and another
layer of thread is wound in and so on until the groove is filled. The glue or varnish
serves to fill up all cracks and crevices and the thread prevents it from falling out or
cracking if it becomes heated. The thread. is disposed in even layers and can be
easily cut through with a knife, thus permitting layer after layer to be readily removed
as the contact surface of the commutator is worn down. As stated, however, any other
suitable insulating material may be used, and it may be inserted in the groove in any
desirable manner.
I use the words "contact surface" in the claims to designate that particular portion
of the commutator against which the brushes are adapted to bear.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is.
1. A commutator in which the contact surface is approximately the same width as
the brushes used therewith substantially as and for the purposes set forth.
2. A commutator provided with a groove or channel to limit the width of its contact
surface, substantially as and for the purposes set forth.
3. A commutator provided with a groove or channel to limit the width of its contact
surface, such groove being filled with insulating material substantially as and for the
purposes set forth.
4. A commutator provided with a groove or channel to limit the width of its contact
surface, such groove being filled with insulating material in separable layers, substan-
tially as and for the purposes set forth.
5. A commutator section B provided with a slot 61, the outer end of said section and
the side of the slot nearest thereto being parallel with each other, whereby a contact
surface of uniform width is provided, substantially as and for the purposes set forth.
Dated this 5th day of August 1890.
Dated this ath day of August 1890.
J. W. EASTON.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.