Improvements in Electric Motors and Dynamos.
Year: 1891

page_text: Date of Application, 17th Nov., 1891-Accepted, 5th Mar.,
1892
COMPLETE SPECIFICATION.
Improvements in Electric Motors and Dynamos.
I, MARTIN CHARLES BURT, a citizen of the United States of America, residing
at 621 Pullman Building, Chicago, in the County of Cook and State of Illinois,
Manufacturer, do hereby declare the nature of my invention and in what manner
the same is to be performed to be particularly described and ascertained in and by
the following statement:-
My invention relates to certain improvements applicable to dynamos or electric
motors, which improvements have for their object, first, certain improvements in
the framework of such machines, whereby a cheap, rigid and powerful frame may
be obtained; second, certain improvements in the construction of armatures and
certain attachments therefor, by means of which the armature, commutator and
coils upon the former, may be kept cool and free from dust and filings, in order
that the maximum efficiency and safety may be attained; and third, certain
improvements in the outside wiring, whereby a single dynamo may be made to do
the work of two or more, and the power of the machine increased to meet the added
requirement of the increased work.
In addition to these main improvements I have also made certain minor improve-
ments; as, for instance, in the mounting of the brushes and other portions, all of
which will be clearly set forth in the following description.
My preferred construction is shown in the drawings presented herewith, by means
of nine figures; of which;
Figure 1 is a perspective of a complete machine;
Figure 2 is a side elevation of the machine with the brushes removed;
Figure 3 is a vertical transverse section in line 3 - 3 of Figure 2 ;
Figure 4 is an axial section of the armature and its bearings;
Figure 5 is a side view of the armature and commutator;
Figure 6 is a detail cross-section, showing the mounting of the brushes;
Figure 7. is a similar section through one of the brushes;
Figure 8 is a plan of one of the brushes, and
Figure 9 is a skeleton view, showing certain improvements in the outside wiring
of the dynamo.
The frame of the dynamo is made up of a solid base, A, having field cores, B,
firmly mortised therein, preferably by casting the base about said cores. Spools, C,
encircle the cores above the base, and pole pieces, D, are secured to the portions
Standards, K1, K2, are
extending above said spools, by means of bolts, c.
bolted to the base, A, and terminate in journal boxes, K, in which a shaft, H,
supporting the armature, is journalled. This shaft is shown as hollow, and one
of the boxes, K, is closed at the end, as seen at the right in Figure 4. The
shaft bears a pulley, o, which is geared to a rotary fan, P, the eduction port
of which leads into a pipe, Q, which passes upward along one of the legs, K',
and empties at Q into the enclosed journal box at that end of the shaft. The
hollow shaft is, itself, closed at the other end, and the portion of the shell within
the armature is perforated, as seen at f, to allow the air from the fan to escape into
the interior of the armature. The armature itself may be provided with a core of
any of the well known forms, providing the same contains openings to allow the air
to pass through to the wires. The form shown here is merely a skeleton, and may
or may not be used, as preferred. Whatever form is used, however, it is preferable
to make it slightly bulging or barrel-shaped, in order that in winding the wires they
may be spread apart more at the portion where the greatest danger is encountered.
To prevent the air which is blown in through the armature shaft, from escaping,

page_text: the ends of the armature coils are enclosed by tight boxes, F, which also add to the
beauty and durability of the machine.
The brushes, L, are carried by a yoke, M, turning freely upon the armature
shaft, which is slit, as seen at 7, and provided with a set screw, m, to take up
the wear and avoid any play upon the shaft. This yoke is secured by appropriate
means to the adjacent journal box, to prevent it from rotating with the shaft.
It is often desirable to change the capacity of the brushes, and it is always
necessary that the same should be perfectly adjustable and placed firmly and
evenly upon the commutator. I have attained all of these objects by means of
a construction which is clearly illustrated in Figures 6, 7 and 8. The yoke, M,
has circular holes in its opposite ends, and is slit through said holes, as seen
in Figure 6: Pins, N, are inserted in these holes and clamped therein by means
of the bolts, n, by means of which the slit portions of the yoke are brought
together. Upon these pins, blocks, g, are mounted, and held in place by set
screws, h. These blocks are slotted in their upper portions to accommodate the
brushes, L, which are held in position by set screws, i, and which are regularly
and evenly pressed upon the commutator by means of springs, k. The brushes
may be adjusted separately, first, by means of the set screw, i, to take up the
wear; second, by means of the set screw, h, to press them firmly upon the com-
mutator and they may be also adjusted all together and uniformly by means of
the bolts, .
When any of the brushes are to be thrown out of action, the set
screw, h, is loosened, and the brush swung away from the commutator and secured
in its new position.
:
It is frequently desirable, in the use of a dynamo furnishing a current for a series
of lights or other work which does not require any particular regulation of the
current, to make use of the same for additional purposes, which require such
regulation and which also entail further work upon the generator. I have provided
means for accomplishing this by double-winding the field cores, interposing a
rheostat in one of the windings, and providing a system of switches, by means of
which the work requiring a regulated current may be thrown into the circuit
simultaneously with the field winding containing the rheostat. Figure 9 illustrates
how this may be done, and shows a series-wound dynamo provided also with a
shunt-winding containing a rheostat, C. The main circuit is indicated by heavy
lines, and the shunt circuit by lighter lines. Commencing with the upper brush,
or the one marked L, the current passes downward to the field coil directly
beneath it, from the bottom of said coil across to the left hand coil, and after
leaving the latter proceeds downward, as seen at a', to a post, a², upon which
swings a switch, Z, capable of connecting the post, a², with either of two posts,
marked and d², respectively. In the drawings the connection is with the
post, 62, and from that the current passes to the circuit, D', thence back to the
post, 2, where it separates, a portion traversing the shunt circuit, 6, and the remainder,
the circuit, B'. From both of these it returns to a post, 63, connected by a
switch,, with a post, c', from which it returns to the dynamo, through the
brush, L. This shows both outside circuits in use, and also the shunt circuit, b',
containing the rheostat, C, by means of which the exciting force of the dynamo
may be regulated. The switch, e, may be swung upon the post, c', to connect the
latter with the post, 62; and to throw both the shunt circuit and the outside
circuit, B, out, both switches are swung to the left, the switch, Z, then resting
upon the post, d, and the switch,, upon this post, 2. The current now leaving
the field coils passes from the post, a², to the post, d², thence through the circuit, D,
back to the post, 62, thence through the switch, r, to the post, c', and back to
the dynamo.
I claim as new and desire to secure by Letters Patent :
FIN

page_text: upon said shaft, tightly closed at the ends and loosely wound between the same;
substantially as described.
2-The combination with an electric dynamo and an outside circuit, of a supple-
mentary shunt-winding upon the field coils, a second outside circuit, and a system
of switches, whereby the shunt-winding and the second circuit may be simultaneously
thrown into or out of operation; substantially as described.
3-The combination with an electric dynamo and an outside circuit, of a supple-
mentary shunt-winding upon the field coils of the dynamo, said shunt circuit
containing means for regulating the resistance, a second outside circuit, and a
system of switches by means of which the shunt circuit and the second outside
circuit may be simultaneously thrown into or out of the first circuit; substantially
as described.
4-The combination, in an electric motor or dynamo, of a hollow armature shaft,
a suitably operated blower having its eduction pipe connected with the interior of
the shaft, openings in the shaft within the armature, and an armature upon said
shaft, tightly closed at the ends and loosely wound between the same; substantially
as described.
A
D 1901
MARTIN CHARLES BURT.
W. H. Beck,
115, Cannon Street, London, E.C.,
Consulting Engineer and Patent Agent.