IMPROVEMENTS CONNECTED WITH THE ELECTRIC LIGHTING OF TRAINS
Year: 1886

page_text: Date of Application, 14th Apr., 1886.
Complete Left, 11th Dec., 1886.
Complete Accepted, 8th Feb., 1887.
We ROOKES EVELYN BELL CROMPTON of Arc Works Chelmsford, & JAMES SWIN-
BURNE of Are Works, Chelmsford, Electrical Engineers, do hereby declare the nature of
our invention for IMPROVEMENTS CONNECTED WITH THE ELECTRIC LIGHTING OF TRAINS
to be as follows:-
One of the difficulties in train lighting is that if the dynamo is driven from the axle
it does not go at a uniform speed. According to our invention the dynamo is driven
off a countershaft which is driven off the axle of a carriage or van. The countershaft
is in the same horizontal plane as the axle so that the movement of the carriage
relatively to the wheels does not affect the dynamo. The dynamo is in connection with
secondary cells. The field magnets are wound with two wires; one is in shunt to the
armature as if the dynamo were an ordinary shunt machine wound to work at a low
speed, say 500 revolutions. The lamps are in shunt to the armature also; but the cells
are so connected up with the second wire that if the dynamo charges them, the
current goes round the field magnets by the second wire so as to demagnetise them.
Thus the dynamo is like a compound machine wound to work with a low speed and
having more main than usual, & that main coupled up backwards, the lamps being in
shunt to the armature only, & the cells in series with the backward-wound main.
The result is that as the speed increases above 500 the dynamo charges the cells but
the pressure on the lamps does not rise much as the field is demagnetised by the
current going to the cells. The second wire is so arranged that at the maximum
speed the cells take their maximum charging current which demagnetises the fields to
the right degree. If the speed falls below 500 the cells begin to help the dynamo by
supplying part of the current to the lamps, and in so doing they magnetise the field.
more strongly, so that the dynamo does not stop giving current till it goes at say 300.
The second wire or backward main is made thick so that there is little loss of pressure
even with a large current to the cells. As the train sometimes stops & sometimes goes
backwards, means must be taken to prevent the current from the cells from burning
the armature up when stopped.
The method we find to answer well in practice is to have a cut-out in circuit to

page_text: break the armature connections when the speed falls below a certain value. The
dynamo is driven in the usual way, so that when the train stops or reverses the dynamo
does so too. In this case the brushes must be shifted on reversal.
To effect this the brush carrier or cross bar is mounted on the axle so as to turn with
it but is held by adjustable stops, so that if the machine goes one way the brushes go
round until the stop holds them in the right position for that direction of rotation, and
if the train goes the other way the brushes are carried about half a revolution until they
come to the other stop. Tangent brushes or brushes that will allow the commutator
to run either way under them are used in carrying out the invention.
A centrifugal or other suitable governor works a cut-out which cuts out the
armature when the speed is too low and puts it in again when high enough. This
governor may also cause the short-circuiting of the backward main when the armature
circuit is broken. This governor may be mounted on the dynamo shaft. Instead of
a speed cut-out, an electric arrangement of well understood character for such purpose
may be used which is actuated by the armature electro-motive force in making circuits
and by the discharge of the cells in breaking it.
There are many ways of doing this by double wound electro-magnets; and the field
magnets may be made to polarise the cut-out.
WM. BROOKES & SON,
55 & 56, Chancery Lane, London,
Agents for the said Rookes Evelyn Bell Crompton
and James Swinburne,

page_text: Improvements Connected with the Electric Lighting of Trains.
We ROOKES EVELYN BELL CROMPTON of Arc Works Chelmsford, and JAMES
SWINBURNE of Arc Works, Chelmsford, Electrical 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 :—
One of the difficulties in train lighting is that if the dynamo is driven from the axle
it does not go at a uniform speed. According to our invention the dynamo is driven
from a countershaft or subsidiary axle which intermediate shaft is driven from the axle
of a carriage or vehicle. The countershaft is in the same horizontal plane as the
driving axle so that the movement of the carriage relatively to the wheels does not
interfere with or affect the dynamo. The dynamo is in connection with secondary
cells or storage battery. The field magnets are wound with two wires, or con-
ductors of electricity one is in shunt to the armature as if the dynamo were an
ordinary shunt machine wound to work at a low speed, say 500 revolutions. The
lamps are in shunt to the armature also; but the cells are so connected up with the
second wire that if the dynamo charges them, the current goes round the field magnets
by the second wire so as to demagnetise them. Thus the dynamo is like a compound
machine wound to work at a low speed and having more main than at present is usual,
and that with the mains coupled up backwards, the lamps being in shunt to the
armature only, and the cells in series with the backward-wound mains. The result
attained by our arrangement is that as the speed increases above say 500 revolutions
per minute the dynamo charges the cells but the pressure on the lamps does not
increase however much the field be demagnetised by the current going to the cells.
The second wire is so arranged that at the maximum speed the cells take their
maximum charging current which demagnetises the fields to the right degree. If the
speed falls below say 500 revolutions per minute the cells begin to aid the dynamo by
supplying part of the current to the lamps, and in so doing they magnetise the field
more strongly, so that the dynamo does not stop giving current until it goes at say
300 revolutions per minute. The second wire or backward main is made thick so that
there is little loss of pressure even with a large current to the cells. As the train
sometimes stops and sometimes goes backwards, means must be taken to prevent the
current from the cells from burning the armature up when stopped.
The method we find to answer well in practice is to have a cut out in circuit to break
the armature connections when the speed falls below a certain value. The dynamo is
driven in the usual way, so that when the train stops or reverses the dynamo does so
too. In this case the brushes must be shifted on reversal. To effect this the brush
carrier or cross bar is mounted on the axle so as to turn with it, but is held by
adjustable stops, so that if the machine goes one way the brushes go round until the
stop holds them in the right position for that direction of rotation, and if the train goes
the other way the brushes are carried about half a revolution until they come to the

page_text: other stop. Tangent brushes or brushes that will allow the commutator to run either
way under them are used in carring out the invention.
A centrifugal or other suitable governor works a cut out which cuts out the
armature when the speed is too low, and puts it in again when high enough
This governor may also cause the shortcircuiting of the backward main when the
armature circuit is broken. This governor may be mounted on the dynamo shaft
Instead of a speed cut-out, an electric arrangement of well understood character for
such purpose may be used which is actuated by the armature electromotive force in
making circuit, and by the discharge of the cells in breaking it. There are many
ways of doings this by double wound electromagnets; and the field magnets may be
made to polarise the cut-out.
Having now particularly described and ascertained the nature of our said Invention,
and in what manner the same is to be performed, we declare that what we claim is.
1. In the electric lighting of trains the employment of a dynamo electric machine
having a backward wound main arranged as and for the purpose substantially as
described.
2. In the electric lighting of trains the employment. in combination of a dynamo
electric machine with a shunt, and a backward main with secondary cells substantially
as described.
3. In the electric lighting of trains the employment of a dynamo electric machine
having its brushes or collectors mounted on a suitable brush holder which can move so
as to set the brushes correctly to position for either direction of rotation of the
armature.
WM. BROOKES & SON,
55 & 56, Chancery Lane, London,
Agents for the Applicants.