Improvements in Electro Motors and Dynamos.
Year: 1897

page_text: Date of Application, 12th Oct., 1897-Accepted, 27th Nov., 1897
COMPLETE SPECIFICATION.
Improvements in Electro Motors and Dynamos.
We, THOMAS BLACKWOOD MURRAY. of 94, Hope Street, in the County of
Glasgow, North Britain, Electrician, and GEORGE JOHNSTON, of the same place,
Consulting Engineer, 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, that is to say:-
-
This Invention has for its object to construct an electro motor which may be
economically and efficiently worked at widely varying speeds and loads whilst
being supplied with continuous current at approximately constant pressure, and
one in which no adjustment of the brushes is required for different speeds and
leads. A part of the improvements is also applicable to dynamos.
The improved motor is constructed with two armatures on the shaft, and each
armature is provided with one or more separate and distinct windings connected
up to their respective commutators. These windings may be of any suitable ring
or drum type; and by connecting up the armature windings in series or in parallel
combinations, lower or higher speeds can be obtained.
By varying the strength of the magnetic field by means of suitable resistances
or other known means, the speed of the armatures can be varied within wide
limits. In ordinary conditions this method is not admissable as it weakens or
destroys the magnetic field necessary for the sparkless commutation of the arma-
We
ture currents, thereby preventing the satisfactory working of the motor.
avoid the difficulty referred to as occuring with ordinary arrangements by provid-
ing a separate field for reversing or commutating such field being practically
independent of the main magnetic field, upon which the speed of the motor
depends. Such separate fields much more conveniently, economically, and
advantageously applied with the two armatures on one shaft than can be done with
a single armature.
And in order that the Invention and the manner of performing the same may
he properly understood we hereunto append a sheet of explanatory drawings
comprising diagrams showing examples of the improved arrangements.
Figures, 1, 2, and 3, of the drawings are a plan, a side elevation, and an end
elevation of one example; and Figures, 4, and 5, are side and end elevations of
another example. In these diagrams the reference letters, N, and S, denote, as
usual the northward and southward poles of the several field electro magnets, and
other letters are severally used to mark the same or like parts wherever they are
repeated.
In the example shown in Figures, 1, 2, and 3,, the shaft, A, has two
armatures, B, C, and there are two main field magnets, D, E, each of which acts
by its opposite poles, N, S, on the two armatures, being arranged so that the
N. pole of each magnet is on the side of the armature opposite to that acted on
by the S pole of the other magnet. These main field magnets, D, E, are not shown
in Figure, 1.
Separate comparatively small electro magnets F, G, are placed so that their
malos may act in the spaces through which the parts of the armatures successively

page_text: pass from the pole of one main magnet to that of the other, the N and S poles of
these separate magnets being placed as shown in the diagrams to suit the direction
of rotation indicated by the arrows. The separate magnets, F, G. are preferably
energised by coils through which current passes to the armatures.
With ring armature winding two reversing magnets, F, G, are required; but
with drum winding it is only necessary to use one.
The improvements are also applicable to multipolar machines; Figures, 4,
and 5, showing the application to an electro motor with four main field magnets.
The additional small magnets, (F,G) may also be applied to a dynamo to ensure
sparkless reversal.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed, we declare that what
we claim is:
In electro motors and dynamos, the combination of two armatures on a shaft.,
with main field magnets each acting with its opposite poles on the two armatures,
respectively, and with additional small magnets each neting similarly and in the
spaces between the poles of the main magnets-substantially as and for the
purposes hereinbefore described.
Dated this Eleventh day of October 1897
EDMUND HUNT
Applicants Agent,