Improvements in Brushes for Dynamos.
Year: 1899

page_text: Date of Application, 17th Mar., 1899-Accepted, 28th Oct., 1899
Improvements in Brushes for Dynamos.
1, CARL ENDRUWEIT, of Tegelerstrasse 15, Berlin, N., in the Empire of Germany,
Manufacturer, 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 aud
by the following statement: -
Dynamo brushes as hitherto used have various faults consisting chiefly in their
hardness and stiffness, which causes wear of the collector, grooving and the like
resulting in unequal current and heavy sparking and necessitating frequent
turning and polishing of the collector. Moreover it is clear that by these dis-
advantages the uncertainty of the working is augmented, a considerable part of
the driving power is lost and more care is required of the dynamo electric
machine.
These disadvantages accrue from the brushes hitherto used consisting of a
mechanical junction of carbon with metal.
This construction cannot have the suppleness and elasticity required for a
perfect brush. Further the carbons of the brushes are sooner worn out than
the metal parts.
In this invention a junction of metal and carbon is effected which gives a re-
sulting product which is equal and elastic and prevents uneven wearing of the
joined materials.
The improved brushes not only avoid the here before mentioned disadvantages
but have the advantage that they polish the collector in consequence of their
suppleness and elasticity and the collector always remains even and smooth thus
reducing repairs and wear to the minimum and prolonging the durability of the
collector. Further the surface of the collector being always smooth and the
whole surface of the brushes lying always on the collector, the delivery of current
takes place absolutely free from sparks with the least possible resistance and a
great working safety.
The method of construction is the following:
So called metal paper, that is galvanically or mechanically produced, sheets
of chemically pure nickeled copper intimately joined with paper or any equiva-
lent substance, is treated so that the non-metallic layer of the metal paper is
saturated with a substance furthering the cohesion and suitable for carbon forma-
tion and is then reduced to carbon by means of dry heat.
The substance above referred to consists of sugar (3 kilograms) graphite (2 kilo-
grams) and gum arabic (50 grams) mixed together in about the quantities men-
tioned and dissolved in boiling water. The substance so obtained is laid on the
paper side of the sheet in a cold state in an equal layer by means of a soft brush.
The sheets remain then till they are entirely dry.
Then the prepared surface is rubbed equally with graphite dust; a large piece
of wool is best used for this purpose.
By this means the metal and carbon is united so intimately that they form an
equal and elastic substance which when made into brushes does not unequally
wear the the collector and gives the above mentioned advantages.

page_text: Having now particularly described and ascertained the nature of this said
invention and in what manner the same is to be performed I declare that what
I claim is
A dynamo brush characterized by alternate layers of thin metal skins prefer-
ably chemically pure and a conductive elastic but non-metallic material, prefer-
ably carbon obtained by carbonizing of organic materials treated preferably
with a liquid favoring the cohesion of the material to be carbonized.
Dated this 17th day of March 1899.
HERBERT HADDAN & Co.,
Agents to Applicant, 18, Buckingham Street, Strand, W.C.