An Improved Material for the Construction of Bearing Surfaces Specially Applicable to the Brushes and Commutators of Dynamo Electro Machines.
Year: 1889

page_text: Date of Application, 15th July, 1839
Complete Specification Left, 15th Apr., 1890-Accepted, 5th July, 1890
PROVISIONAL SPECIFICATION.
An Improved Material for the Construction of Bearing Surfaces
Specially Applicable to the Brushes and Commutators of Dynamo
Electro Machines.
I KILLINGWORTH WILLIAM HEDGES of 25 Queen Anne's Gate, Westminster,
Electrical Engineer, do hereby declare the nature of my said invention to be as
follows:-
My invention relates to the manufacture of a new material for rubbing or bearing
surfaces composed of a mixture of carbon, and mica, or steatite, and can be applied
to diminish friction as in the case of the bearings of shafts, dynamos &c., or it may
be employed for the purpose of collecting the electric currents from the revolving
commutator of a dynamo.
To prepare my material I take finely powdered carbon or graphite, and to it add
a suitable proportion of powdered mica or stentite, and after incorporating the mass
with tar, sugar, or any material that will carbonise with heat, press the inisture
into moulds of the desired form, and bake the material in the same way as if carbon
alone was used. The proportion of mica inay be varied according to the density
which it is desirable to make the block and according to whether the material is to
be used as a conductor of electricity or not. When used as a step or bearing a much
larger proportion of mica can be used than when the substance is to be used as a
conductor of electricity on account of the high insulating property of the mica.
When I use the material for the brushes of dynamos I prefer forming the carbon
and mica into plates or rods, and in order to reduce the electrical resistance I insert
metallic wires or strips in the material or I electroplate the same, and when several
plates rods or strips are mounted side by side in the same holder I connect them all
together by wire gauze passing through the body of each plate, rod, or strip, which
may be very conveniently effected by embedding the metallic gauze in the material
and baking the whole. By this means the brush is made more elastic and accom-
modating and the conductivity is improved.
It is not necessary for the metal touch the commutator, but if it does so it will
wear down with the carbon. A brush so formed may be employed in the same way
as the ordinary copper brushes.
Although I have described the application of my carbon material to the brushes of
a dynamo, it can be also applied to the plates or segments of the commutator and
used with ordinary copper brushes or with those of the carbon material.
As oil, which is practically speaking an insulator, is not used with bearings of this
description, the shaft of a dynamo and the bearing are in good electrical connection,
and consequently the current coming from one end of the wire in the commutator
may pass through the bearing to a terminal on any part of the machine in electrical
connection with the bearing.
2000

page_text: COMPLETE SPECIFICATION.
An Improved Material for the Construction of Bearing Surfaces
Specially Applicable to the Brushes and Commutators of Dynamo
Electro Machines.
1 KILLINGWORTH WILLIAM HEDGES of 25 Queen Anne's Gate Westminster
Electrical Engineer, do hereby declare the nature of my said 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 in part to the manufacture of a new material for rubbing
or bearing surfaces composed of a mixture of carbon, and mica, or steatite, and can
be applied to diminish friction as in the case of the bearings of shafts, dynamos &c.
or it may be employed for the purpose of collecting the electric currents from the
revolving commutator of a dynaino.
To prepare my material I take finely powdered carbon or graphite, and to it add
a suitable proportion of powdered mica or steatite, and after incorporating the mass
with tar, sugar, or any material that will carbonise with heat, I press the mixture
into moulds of the desired form, and bake the material in the same way as if carbon
alone was used. The proportion of mica may be varied according to the density
which it is desirable to make the block and according to whether the material is to
be used as a conductor of electricity or not. When used as a step or bearing a much
larger proportion of mica can be used than when the substance is to be used as a
conductor of electricity on account of the high insulating property of the mica.
When I use the material for the brushes of dynamos I prefer forming the carbon
and mica into plates or rods and in order to reduce the electrical resistance I insert
metallic wires or strips in the material or I electroplate the same. The method
which I employ to hold the rods or plates is to pass each one through a tube or
suitable holder, the tubes or holders lying parallel to each other and being held in
some frame of suitable shape which will allow each tube or holder a certain amount
of play, the object being to allow each rod or plate to be adjusted lengthwise
independently of the others and also at right angles to its length so ns to bear
uniformly on the commutator.
It is not necessary for the metal to touch the commutator, but if it does so it will
wear down with the carbon. A brush so formed may be employed in the same way
as the ordinary copper brushes.
My Invention also relates to the following system of constructing brushes.
When several plates rods or strips are mounted side by side in the same frame or
holder, I sometimes connect them all together by wire gauze passing through the
body of each plate, rod, or strip which may be very conveniently effected by embedding
the metallic gauze in the material and baking the whole. By this means the brush
is made more light and accommodating and the conductivity is improved.
The arrangements above described are also applicable to brushes composed of carbon
alone.
Although I have described the application of iny carbon material to the brushes
of a dynamo it can he also applied to the plates or segments of the commutator and
used with ordinary copper brushes or with those of the carbon material.
As oil, which is, practically speaking an insulator, is not used with bearings of this
description, the shaft of a dynaino and the bearing are in good electrical connection,
consequently the current coming from one end of the wire in the commutator may
pass through the bearing to a terminal, on any part of the machine in electrical
connection with the bearing.
My Invention is especially applicable to the bearings and rubbing surfaces of
light machines, such as sewing machines, bicycles &c. the metal part can be fitted
with a removable bush which can be easily replaced when worn and the advantages
of not having to use oil is apparent.
In the drawings accompanying this Specification Figures 1 and 3 I have diagram-

page_text: matically shown different forms of brushes and holders for use with dynamo machines
in place of the ordinary arrangements.
In fig. 1 the brush is represented as being composed of rods (a) of the carbon
material electroplated with copper which are placed in tightly fitting tubes (b)
preferably of copper or brass, the tubes being held in a frame not shown in a manner
which will allow of a certain amount of elasticity between each tube. As the
carbon material wears away the rods can be pushed further through the tubes and
will adjust themselves so as to bear uniformly on the commutator.
In fig. 2 another arrangement is shewn in which the brush is composed of strips
of the carbon material in the body of which a metallic plate, preferably of wire
gauze, or perforated sheet metal has been embedded, as shown by the thick black
line, which wears away with the brush; this metallic plate or gauze is inserted in
order to join the strips and to improve the electric conductivity.
Fig. 3 represents the commutator of a dynamo on which a brush is resting, the
segments may be partly or wholly made up of the carbon material, as shown by the
shaded segments.
:
Fig. 4 & 5 represent an alternating current dynamo the bearing in which the
shaft runs being made of the carbon material, which is shewn at (a) shaded black.
The carbon material may be shaped so as to go into an ordinary plummer block.
As shown in figures 4 and 5 a cylinder of the requisite form is fixed inside a split
copper tube (c) this being held in the ordinary iron bearing by a cap which can
be bottled down in the usual manner, so as to hold the copper and carbon tightly in
place.
The current from the armature of the dynamo is passed through the carbon
bearing (c) the wires of the armature being connected to the shaft as shewn at (e)
and (e) the bearings must be insulated one from the other, to prevent a short circuit;
the insulation of the two parts of the shaft is shown at (d) and the insulation of the
base at (d). The current will be led to the terminal as shewn.
Fig. 6 represents a bearing where the carbon material is used as a bush, and is
particularly applicable to small bearings the black portion (a) is the carbon material
in which the shaft runs, this may be made corrugated, or have lugs, on the outside
so as to prevent it turning in the copper tube (c). The copper tube may be made
slightly taper and be split and have a screw cut on the outside, and the metallic
block may be tapped, so that when the copper tube, containing the carbon core, is
screwed into the inetallic block the core will be compressed and thus will be held
fast.
Having now particularly described and ascertained the nature of my said Inven-
tion and in what manner the same is to be performed, I declare that what [
claim is
First. I claim as my Invention the preparation of a new material suitable for
bearings, brushes, cominutators &c. from a mixture of carbon and mica or steatite or
their equivalents substantially as described.
Second. The hereinbefore described method of employing the carbon material or
ordinary carbon to collect the current from dynamos substantially as shewn in
Figures 1. 2 and 3 of the accompanying drawings.
Dated 15th April 1890
Dated 15th April 1890.
GEO. DOWNING,
8, Quality Court, London, W.C., Agent for Applicant.