Improvements in and connected with Carbon Brushes for Dynamo Electric Machines or Motors.
Year: 1898

page_text: COMPLETE SPECIFICATION.
1
Improvements in and connected with Carbon Brushes for Dynamo
Electric Machines or Motors.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by Albert L. Rohrer,
residing at Schenectady, in the County of Schenectady, State of New York, United
States of America, Electrical Engineer), and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement;
The present invention relates to connecting conductors to carbon brushes for
dynamo-electric machines or motors; and has for its object to provide an efficient
contact for the conductor which shall enable it to carry without undue heating
the full current transmitted to the brush. The process of uniting the conductor
and the brush is also embraced within the invention. It has been a common
practice in the art to transmit the current from brushes by contact, a spring or
plate being pressed against the brush; this has not been efficient, the contact not
being sufficient, unless of very large area, to carry the current to the brush;
when made of sufficient area, the device has been clumsy and uncommercial.
Another method of making connection between the brush and the flexible con-
ductor commonly used to carry the current has been to bore a hole in the brush
and insert in that a plug of solid conducting metal, to which the flexible con-
ductor has previously been secured. This has not been, however, a good form
of connection except for small brushes, the main difficulty being to drill the hole
in the carbon brush in such shape that the plug may be made to fit it. It is diffi-
cult, on account of the softness of the carbon to bore the hole without making
it taper towards the bottom, and in many cases the plug will only make good con-
tact at or near the bottom of the hole. Various other forms of connection have
been devised, but none, have proved thoroughly efficient.
To overcome the difficulties pointed out, the present invention has been devised
one part of which consists in a clip designed to fit over the outside and top of
the brush and to which the conductor has previously been secured.
This clip
is soldered firmly to the brush and the joint is afterwards electro-plated with
copper or other good-conducting metal. Of course the brushes as is the common
practice, are previously electro-plated with copper, at least at the portion at
which the clip is connected. Preferably also the sides of the brush over which
the clip fits are cut away so that the outer surface of the clip and the main body
of the brush are in the same plane, and thus the latter may slide easily in the
box commonly provided for it on the brush holder.
Another part of the invention consists in the process or uniting the brush
and clip, presently described more fully.
The accompanying drawings show my invention, Fig. 1 being a perspective
view of the brush with the clip about to be applied thereto, and Fig. 2 being a
similar view of the completed article of manufacture.

page_text: In Fig. 1, A is the brush, a, a, are the parts of the sides which are cut away
to take the clip B; the latter is formed with a loop bin which the flexible con-
ductor C is compressed and soldered. The form of the clip B is such as to
just make a snug fit with the cut-away portion a of the brush. In practice in
the manufacture of the brushes, they are first coated with hard solder, as indicated
in the unshaded portion of Fig. 1, over that part of the brush which will be
covered with the clip B. The latter is then applied and held firmly while soldered
in place, the whole end of the brush and clip being heated in any desired manner
to effect this; the surplus solder is then brushed off and the brush cooled so that
the clip adheres to it firmly. Afterwards if necessary the joint is electro-plated
with copper or other good conducting metal, copper of course being preferred.
By the construction 'outlined a thoroughly' good contact is obtained of ample
area to carry any current which the brush itself is designed to transmit.
The contact never becomes impaired during the life of the brush, and so far
as known, it has corrected all the principle difficulties attending the use of
carbon brushes for the transmission of current.
Having now particularly described, and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same
is to be performed, we declare that what we claim is:-
1The process of uniting a carbon current collector brush to a metal conductor,
consisting of plating the brush with a suitable metal, and then soldering to the
metal plating a clip to which the conductor has previously been secured.
2-The process of connecting a carbon current collector brush to another con-
ductor, consisting of plating the brush with a suitable metal, fitting thereto a
clip of good conducting sheet metal, soldering the clip in place upon the brush,
and plating the joint and adjacent parts with conducting metal, such as copper.
3--The means described for carrying current from the carbon brush to the stud
in a brush-holder, consisting of a flexible conductor provided with a clip making
a close fit with the brush.
4 The conductor C having the strip B provided with a loop b, in which the
conductor is compressed and soldered.
5-The combination of a brush having a cut-away portion a with a strip of
conducting material registering with the cut-away portion, so that the strip and
sides of the main body of the brush are in the same plane, and a conductor
attached to the strip.
As a new article of manufacture, a carbon current collector brush having
a cut-away portion a designed to register with a conducting strip for collecting
current.
A carbon current collector brush having a cut-away portion, and a rect-
angular clip of good conducting metal soldered to the cut-away portion of the
brush, with a flexible conductor secured in a loop in the strip.
8-A carbon current collector brush having a cut-away portion, a clip soldered
to the cut-away part of the brush, the joint being electro-plated with copper,
and a clip having a loop in which a flexible conductor is compressed and soldered.
Dated this 18th day of October 1898.
THE BRITISH THOMSON-HOUSTON CO. LTD.,
W. MARTINDALE,
A. R. MONKS,
Directors,
ALFRED CLEMENTS,
Assistant Secretary.