System for the Automatic Regulation of the Position of the Brushes of Dynamo-electric Machines, Magneto-electric Machines, and Electric Motors.
Year: 1891

page_text: Date claimed for Patent under Sect. 103 of Act,
being date of first Foreign Application (in
Switzerland),
-31st Dec., 189C
Date of Application (in United Kingdom), 23rd July, 1891
Complete Specification Left 23rd July, 1891-Accepted, 19th Sept., 1891
COMPLETE SPECIFICATION.
A System for the Automatic Regulation of the Position of the
Brushes of Dynamo-electric Machines, Magneto-electric Machines,
and Electric Motors.
We, HERMANN CUÉNOD, ERNEST SAUTTER, and GEORGES HOCHREUTINER,
together constituting the firm of Cuénod, Sautter and Company, of Geneva,
Switzerland, Engineers, 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 :—
In every dynamo electric machine the current circulating in the armature creates
a flux of force which reacts upon the magnetic field and displaces it. It con-
sequently results that the brushes should be shifted a certain distance corresponding
to the intensity of this re-action. If this displacement be not made the brushes
short circuit the sections of the winding cutting the lines of force and bright
sparks are produced which are extremely injurious to the collector and to the
brushes.
This effect is not felt at the terminals of machines excited in series, because the
magnetic field gains almost proportionally with the current, but it is strongly
manifested in machines and motors with shunt or separate excitement.
neutralized in these machines by a second winding fixed against the polar masses
It may be
in the interspace, this winding being traversed by a current producing the same
magnetic re-action as that produced by the armature itself, but this is not always
practicable or even possible.
The object of our invention is to obtain automatically a precise adjustment of
the brushes to the line of commutation.
Our system consists of the combination with one of the collecting brushes of the
dynamo of two telltale brushes placed the one in front, the other in rear of the
said brush and combined with an arrangement of any sort such that a difference
of tension existing between the two telltale brushes may produce the necessary
displacement of the collecting brushes to replace these last to their normal
position.
This system may be realized by various constructive arrangements of which we
give two examples in the annexed drawing. The apparatus (Figure 1) is com-
posed in principle of two telltale brushes & placed the one in front and the other
behind one of the principal brushes B B which require to be regulated. The two
brushes bb' are connected to the armature of a small motor M separately excited.
This motor M governs the brush carrier O by means of a train of gear e and of a
toothed segment O', and can be turned in one direction or the other around the
axis of the dynamo according as the current traverses the armature in one direction
or the other.
The telltale brushes bb' are adjusted in such a manner that in mean position the
principal brush B is exactly adjusted upon the line of commutation, there is then
no difference of tension between 6 and b'. In these conditions the motor remains
at rest.

page_text: As soon as displacement of the line of commutation occurs this line approaches
one of the telltale brushes and recedes from the other. Immediately a difference
of potential between the two is established and the passage through the small
motor M of a current from one telltale brush to the other results. The motor M
commences to run and operates until all difference of tension is removed, that is
until B is again adjusted to the line of commutation.
to say,
Figure 2 shows an arrangement for the indirect control of the motor M per-
mitting of greater exactitude of regulation. The two conductors passing from
the telltale brushes bb' are connected to a very sensitive relay I with a polarized
armature. This relay I governs in turn the motor M by a two contact arrange-
ment. Then the least change of position of the line of commutation determines
the action of the regulating motor.
The Figures 3, 4 and 5 are diagram views showing clearly the manner in which
the current changes in sign from one telltale brush to the other according as the
line of commutation is displaced forward or backward in relation to the principal
brush.
Figure 3 shows the brushes exactly adjusted upon the line of commutation. In
this case there is no reason for a current to circulate from one telltale brush to the
other. The motor remains at rest.
Figure 4 shows the brushes in advance of the proper adjustment. The left
hand telltale brush approaches the line of commutation, that is to say, the point
in the collector where the tension is highest. The telltale brush 6' recedes there-
from, whence results the establishment of a difference of tension between the two
and the motor utilizing this difference continues to run until equilibrium is
re-established.
Figure 5 shows the brushes behind the proper adjustment. The same effect is
produced but in the opposite sense; 6' approaches the pole +, & recedes from it;
consequently current from b' to b. The motor runs in the opposite direction and
brings back the brushes B B to the line of commutation, when the equilibrium is
re-established between b and b¹.
It is not necessary to employ an electric motor to control the brushes. The
employment of the relay allows of the use of mechanical gear utilizing either the
movement of the dynamo to be regulated or an exterior force of any sort. For
example a very simple reversing movement may be obtained either by means of
cones, or of friction pulleys, or it may be, by means of tangent screws, gearing or
even by a cord connection or rope or running cable or three pulleys, two fixed and
the other an idle pulley by means of fork gearing or any other. These mechanical
arrangements may be varied indefinitely, it is not possible to describe all of them.
Also it is evident that the independent adjustment of each principal brush of a
dynamo may be effected by the arrangements above described.
We claim as being of our invention :—
A system of automatical regulation of the brushes of dynamos to the line of
commutation, consisting in principle of two telltale brushes placed the one in front
and the other behind one of the brushes to be regulated and combined with an
arrangement of any sort such that a difference of tension occurring between the two
telltale brushes produces the necessary displacement of the connecting brushes to
cause these to be brought back to their normal position.
D10T11001
CARPMAEL & Co.,
Agents for the Applicants.