Improvements in Brushes for Dynamo-electric Machines.
Year: 1884

page_text: Improvements in Brushes for Dynamo-electric Machines.
I, GEORGE HOOKHAM of New Bartholomew Street Birmingham in the County
of Warwick, Electric Engineer, do hereby declare the nature of said invention
for IMPROVEMENTS IN BRUSHES FOR DYNAMO-ELECTRIC MACHINES" to be as
follows:-
11
My improvement is especially applicable to tangential brushes such as are used
with the well-known Siemen's continuous Current Dynamo.
Instead of allowing the brush itself to come in contact with and rest upon the
commutator, I insert between it and the commutator a strip of thin sheet copper
or other metal of about the same width as the brush. This piece of thin sheet
metal is made to lie as flat as possible against the brush proper, and is of such
flexibility that the pressure of the wire brush ensures its contact with the com-
mutator throughout the whole or nearly the whole width of the brush. The strip
of copper passes through a slit in the brush holder below the brush, and is held in
position by a clamping screw. Whenever it may be desired, the copper strip can
be moved forward, so as to bring a fresh or unworn portion of it into contact with
the commutator, and the part which in consequence projects beyond the wire
brush may be cut off with scissors. It is not necessary, however, that this should
be done immediately; so that the re-adjustinent can be made while the machine
is running, the projecting piece being left to be more conveniently removed when
the machine is at rest. A considerable length of copper strip may be used; and
in some cases I use it coiled into a roll on the side of the brush-holder further
from the commutator.
Instead of the ordinary copper-wire brushes I prefer in most cases a single layer
of strips of watch-spring steel laid parallel side by side. Such a brush is less liable
to accidental damage. .
In some cases, to ensure equal pressure all along the commutator I divide the
copper strip to a greater or less extent by short slits in the direction of its
length; but as a rule I prefer to use a strip so thin that this is not necessary.
The strip of copper may be pressed against the commutator by any suitable
spring or pad in place of a tangential brush of wire or spring steel. Or the
Uning H77

page_text: brush-holder may consist of two rollers one above and one below the line of
contact of the metal strip and the commutator. The strip being strained between
them is pressed by this strain against the commutator; the strip being unwound
from the one roller and wound on to the other when it is desired to bring a fresh
portion into contact with the commutator.
GEORGE HOOKHAM.
By Henry Skerrett,
6, Livery Street, Birmingham,
Agent to the Applicant.
1
Improvements in Brushes for Dynamo Electric Machines.
I, GEORGE HOOкHAм of New Bartholomew Street, Birmingham in the County
of Warwick, Electrical Engineer, do hereby declare the nature of said invention
for "IMPROVEMENTS IN BRUSHES FOR DYNAMO ELECTRIC MACHINES," and in what 1
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :—
My improvement is specially applicable to tangential brushes such as
used with the well known Siemens continuous current Dynamo.
are
Instead of allowing the brush itself to come in contact with and rest upon the
commutator, I insert between it and the commutator a strip of thin sheet copper
or other metal of about the same width as the brush. This piece of thin.sheet
metal is made to lie as flat as possible against the brush proper, and is of such
flexibility that the pressure of the wire brush ensures its contact with the com-
mutator throughout the whole or nearly the whole width of the brush. The strip 2
of copper passes through a slit in the brush holder below the brush, and is held in
position by a clamping screw. Whenever it may be desired, the copper may be
moved forward, so as, to bring a fresh or unworn portion of it into contact with
the commutator, and the part which in consequence projects beyond the wire.
brush may be cut off with scissors. It is not necessary, however, that this should 3
be done immediately; so that the re-adjustment can be made while the machine
is running, the projecting piece being left to be more conveniently removed when
the machine is at rest. A considerable length of copper strip may be used; and
in some cases I use it coiled into a roll on the back side of the brush-holder further
from the commutator.

page_text: Instead of the ordinary copper wire brushes I prefer in most cases a single
layer of strips of watch-spring steel laid parallel side by side. Such a brush is
less liable to accidental damage.
In some cases, to ensure equal pressure all along the commutator I divide the
copper strip to a greater or less extent by short slits in the direction of its length;
but as a rule I prefer to use a strip so thin that this is not necessary.
The strip of copper may be pressed against the commutator by any suitable
spring or pad in place of a tangential brush of wire or spring steel. Or the brush
holder may consist of two rollers one above and one below the line of contact of
the metal strip and the commutator. The strip being strained between them is
pressed by this strain against the commutator; the strip being unwound from the
one roller and wound on to the other when it is desired to bring a fresh portion
into contact with the commutator.
I will now proceed to describe with reference to the accompanying Drawings
the manner in which the same is to be performed.
Figure 1 is a side elevation of a tangential brush, and brush holder constructed
according to my invention. Figure 2 is a longitudinal vertical section of the
same. Figure 3 is a plan of the underside of figure 1, showing the parallel strips
of steel, which constitute the brush. Figure 4 is a plan of the upper side of
the said brush and holder. Figure 5 is a transverse section on the dotted lines A B
figure 1.
'
To ensure equal pressure all along the commutator, the copper strip may be
split or divided in the direction of its length as represented in figure 6. Figure 7
represents a modification of brush holder, consisting of rollers with strip metal
wound around, and stretched between the rollers, each brush having two rollers one
above and one below the line of contact between the strip and the commutator.
The same letters of reference indicate corresponding parts in the several figures
of the Drawings.
a is the brush, consisting of parallel strips of steel lying side by side and
soldered to a metal plate f clamped within the holder b. c is a strip of thin sheet
copper or other metal of the same width as the brush, which is interposed between
the brush a and commutator d, so to prevent the brush from coming into direct
contact with the commutator surface. This piece of thin sheet metal lies as flat
as possible upon the brush, and is of sufficient flexibility to ensure its perfect
contact with the commutator throughout the whole, or nearly the whole width,
by the pressure exerted by the separate steel springs of which the brush is com-
posed. is a slit or opening passing from front to back of the holder wherein the
brush and the length of sheet copper c are clamped and held by the screwing up
of the clamping screw e through the screw box b³. f is a metal plate to which the
steel springs are soldered, and is best seen in figure 2, the holder is attached to
the machine by means of the affixing screw g taking upon a spindle passing
through the hole 6 in the body of the holder.
The copper strip c can be moved forward, so as to bring a fresh or unworn
portion of it into intimate contact with the commutator, and the worn part which
projects beyond the steel brush a inay be removed or cut off when the machine is
at rest.
When a considerable length of copper strip is used, I prefer to coil it into a roll cª
on the back side of the brush holder as shown in dotted lines figure 2.
Although I have only described and illustrated the steel spring brush which
I prefer yet an ordinary Siemens wire brush may be substituted for it without any
other change.
In the modification shown in figure 7, the brush consists of two rollers hone
below and the other above the commutator, a strip of sheet copper c being wound.
upon them The strip c is strained between the rollers, and is pressed into intimate
contact with the commutator, the strip being unwound from one roller and wound
on to the other, when it is desired to present a fresh portion of the strip to the
commutator surface. The dotted lines represent the worn portion of the strip.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is
First. Interposing between tangential brushes and commutators of dynamo
electric machines, a strip of sheet metal of about the width of the brush and
capable of being moved forward independently of the brush substantially as
'described and illustrated in figures 1 and 2 of the accompanying Drawings.
j
Secondly. Making tangential brushes of dynamo electric machines from short
lengths of spring steel laid parallel side by side substantially as described and set
'forth in figure 3 of the accompanying Drawings.
Thirdly. The improvement in brushes and brush holders consisting of rollers
and sheet metal disposed and arranged substantially as described and set forth in
figure 7 of the Drawings.
•