IMPROVEMENTS IN REGULATING CURRENTS FROM VOLTAIC CELLS AND TO AND DOW SECONDARY D
Year: 1882

page_text: LETTERS PATENT to William Edward Ayrton Professor of Technical Physics;
Fellow of the Royal Society, and John Perry Professor of Mechanical
Engineering and Applied Mathematics in the City & Guilds of London
Technical College, Finsbury in the County of Middlesex for an Invention of
IMPROVEMENTS IN REGULATING CURRENTS FROM VOLTAIC CELLS AND TO
AND
DOW SECONDARY D
PROVISIONAL SPECIFICATION left by the said William Edward Ayrton
and John Perry at the Office of the Commissioners of Patents on the
23rd September 1882.
WILLIAM EDWARD AYRTON, Professor of Technical Physics, Fellow of the Royal
Society, and JOHN PERRY, Professor of Mechanical Engineering and Applied
Mathematics in the City & Guilds of London Technical College Finsbury in the
County of Middlesex IMPROVEMENTS IN REGULATING CURRENTS FROM VOLTAIC
CELLS AND TO AND FROM SECONDARY BATTERIES WHEN BEING CHARGED AND
DISCHARGED AND IN APPARATUS CONNECTED THEREWITH
When a variable number of Voltaic Cells or a Variable number of Secondary
Batteries are being charged or discharged it is usual to have the cells arranged
so that the positive pole of one Cell and the negative pole of the next are
permanently connected together and the insulated studs of the commutators are
respectively connected with these junctions of positive and negative poles so that
two moveable contact pieces which are attached to the two ends of any circuit enables
their being placed one on any one of the studs of the commutator and the other on
any other one of the studs, and so that all the cells existing between these two
studs in question are charged or discharged through the circuit of which we have
spoken. Now, as the number of cells is altered by the sliding or rolling of one or
both of the contact pieces, either the contact piece leaves one stud completely
before it touches another in which case the circuit is temporarily broken and the
current interrupted, or else the contact piece before entirely leaving one stud

page_text: touches the next In this latter case the circuit is not interrupted but the cell
or cells which are being added to or subtracted from the circuit are temporarily
short-circuited through the contact pieces and are consequently damaged or at any
rate most unnecessarily discharged and highly injurious sparking occurs.
Now our Improvement consists in substituting for each of these single movable
contact pieces a contact maker consisting of two or more metallic pieces which
together form the contact maker and which are connected together through a
resistance coil or coils which moves or move with them. One only of these contact
pieces of each contact-maker is connected with one end of the circuit referred to
above and through which the cells are charged or discharged. When a contact
maker consists of two contact pieces they are so arranged that when they are
moved together neither of the contact pieces can touch two adjacent studs of the
commutator at the same time but the front one touches the stud in advance
before the hinder leaves the stud which is being left. Hence first the circuit is
not broken; and secondly the cell or cells that are being added or subtracted
are not short circuited; and further as they are added to the main circuit,
first, through the resistance coil and secondly, directly, the alteration in the current is
more gradually produced than is the case with the ordinary forms of commutators
Another plan we adopt is to make both the going and return wire of the circuit
through which the cells are to be charged or discharged double, and in place of
connecting the two movable contact pieces by a resistance coil as previously
explained we attach the two ends of the going wire respectively to the contact
pieces of one contact maker and the two ends of the return wire respectively to
the contact pieces of another contact maker so that when either contact maker is
moved the cell added or subtracted is not temporarily short circuited but is
temporarily allowed to send a current through the whole of the going wire or
through the whole of the return wire either of which even in the case of a
comparatively short circuit would have a considerable resistance compared with
that of an accumulator.
It is obvious that the two contact pieces forming the contact maker may be
metallic sliding pieces or metallic rollers or rolling metallic brushes something like
a common rotating barber's brush in construction or they may be wheels with
metallic projections fitting into concavities in the studs or into mercury cups.
When we use sliding contact makers each contact piece of which this contact maker
is ormed may be pressed down with an independent spring which may be a spiral
spring or may be a flat spring which catches a sliding spring by a slot at its end, the
sliding piece having a feather so that there shall be a proper distribution of
pressure and no tendency to tilt at one edge.
The studs of the Commutator may be flush with a surface of wood or other
insulating material which forms the strong backing of the instrument or the studs
may project above the wood a stop being attached to each piece of the contact
maker to prevent it sinking much below the level of the upper surface of the stud
when it is between two studs of the Commutator.
When two or more sets of Cells or Accumulators in series have to be charged or
discharged in parallel circuit the plan we employ consists in connecting the corre-
sponding Cells in each of the rows with separate studs of the Commutator and
using a single moveable contact piece which is large enough to touch at the same
time as many studs as there are rows of Cells used in parallel circuit. If then the
contact piece be moved on, the additional Cell is added to or subtracted from
successively each of the rows and at no time is the circuit broken or the Cell short
circuited. Another advantage possessed by this method is that although the Cells
are charged and discharged in parallel circuit corresponding cells in the various
rows are not connected together except when they are terminal cells of the series
employed and even then only when charging or discharging takes place. This
prevents the wasteful discharging of good Cells through any others which from being
short circuited or otherwise have a lower electro-motive force than the remainder.
The second part of our Invention relates to the method of charging and

page_text: discharging accumulators to enable a constant amount of electrical power to be given
to the lamps or motors in spite of variation in the source employed to charge the
Accumulators.
When any mechanical source of power which varies in its speed is employed in
the driving of a Dynamo Machine the current from this Dynamo Machine being
used for the charging of accumulators or working of Motors we find it possible
to give a nearly constant amount of power to the Lamps or Motors in spite of
variation in the source of power. Our arrangement is suited to cases in which the
direction of motion of power may be opposite and may be varied with any degree
of fluctuation and our arrangement is automatic in its character but differs in the
details depending on the rate at which the energy is being stored in the
Accumulators.
First let us take a case in which the rate at which energy is being stored in the
accumulators is not great in comparison with the rate at which energy is being
supplied to the Motors or Lamps. This would apply where the time during which
the Accumulators have alone to supply electric energy is small compared with the
time during which they are being charged. In such a case one of our methods
consists in fixing the brushes of our Dynamo to a frame which is constrained by
springs to place itself near the mean position in which the brushes are not making
contact with the external circuit which occurs as long as it is only the friction of
the rotating commutator which is acting; but on this frame we have a cylindric
piece P which is concentric with the spindle of the Machine and there is a Mass M
attached to this spindle by means of a spring arranged so that at any speed of the
Dynamo Machine greater than a certain definite speed this mass presses outwards
by centrifugal force against the inner surface of P and its friction with P causes
the brush frame to move round in the direction of rotation so that the brushes now
make contact with the external circuit and at the same time the necessary amount
of lead is given to the brushes at their points of contact with the Commutators.
Further the greater the speed the greater the amount of lead given to the brushes.
When the speed diminishes below a certain amount the frame carrying the
brushes gets nearer the mean position and there is no longer contact with the
external circuit and when the direction of motion is reversed the lead of
the brushes is also reversed and at any speed above a certain limit contact is
established in the opposite direction the lead of the brushes as before increasing
with the speed.
Another plan we employ is to use a governor somewhat like a steam-engine
governor so arranged that the more the balls fly out the greater is the lead given
to the brushes also that the direction of rotation of the governor by causing a catch
to engage in one or other of two stops causes the lead to be given to the brushes in
the right direction. When the balls fly out less than a certain amount the brushes
are taken off the commutator so that at all speeds less than this the dynamo circuit
is interrupted
Now the accumulators are supposed to be arranged in series and joined up to the
studs of one of our commutators mentioned in the first part of this specification
and the terminals of the dynamo machine are joined to two contact makers A and B
resting on these studs so that when the Dynamo is delivering a current some or all
of this current is employed in charging those Accumulators whose studs lie between
these two contact makers. The Lamp or Motor circuit terminates in two other
contact makers C and D which can also slide or roll on the studs or be permanently
connected with certain studs. A and B for example may be attached to the ends
of two arms which enable them to receive the required sliding motion. Now we
allow any suitable form of speed governor to actuate these two arms in such a way
that, when the speed of the Dynamo diminishes the arms are brought closer together
so that there is a less number of Cells being charged and when the speed increases the
arms are separated so that a greater number of cells are being charged. Hence what-
ever be the speed of the Dynamo it can be so arranged that a current is never sent back
through it by the accumulators. Now it is obvious that if the field magnets of the

page_text: dynamo have cores which are made partly of cast iron or of steel some of the cells will
be charged with electricity at any of the very different speeds at which we assume
that our dynamo can deliver a current. With this apparatus we usually combine
an arrangement which causes the two arms to rotate as if they were fixed together
and such that when the arm reaches the last stud of a Commutator it pushes against
a top heavy lever which reverses the direction of motion, the two arms now moving
In this way
'slowly in the opposite direction to that in which they moved at first.
.
we effect a partial equalisation in the charging of the cells at the lower speeds.
Second Let us now take a case in which the rate at which energy is being
stored in the accumulators is comparable with the rate at which energy is being
supplied to the Motors or Lamps. This applies where the time during which the
accumulators have alone to supply electrical energy is comparable with the time
during which they are being charged as for example in the case of electrically
lighting the Metropolitan Railway trains, the source of power being the motion of
the railway carriage the rotation of the wheels of which turns a dynamo machine
on the train which when running supplies more than enough electrical energy to
light the Lamps, the residue (which, in consequence of the times of the stoppage of
the train being nearly equal to the time of running must be nearly half the total
amount of electrical energy produced by the Dynamo) being stored up in the
accumulators and which residue is employed in keeping the lights burning when
the train is going slowly or stopping.
In such a case we find it necessary to effect a re-arrangement of the Accumulators
when starting or stopping the above mentioned automatic apparatus being unable
to produce even an approximately constant supply of electricity to the lamps. In
this case we may or may not employ the automatic adjustment of the charging
handles previously described but the more important object which we effect is the
automatic rearrangement of the accumulators This will be better understood by
taking a simple case- -Suppose that the Dynamo Machine when delivering a current
is run at a nearly constant speed then when the stoppages are as long as when it
is running it is clear that the amount given to the lamps by the dynamo during
running must be equal to that given to the Accumulators. Hence the difference
of potential maintained at the terminals of the accumulators when the dynamo is
running must be much greater than the electromotive force of the accumulators
themselves in order that sufficient charging current may be sent into the accuniu-
lators. On the other hand the difference of potential at the two points in the
accumulator circuit which are attached to the lamps must be that suitable for
causing the carbons to incandesce. Further these two points must be at the end of
the accumulators otherwise a current sent through the terminal cells and which
would have to be sufficient to light the lamps as well as to charge the remainder
would be far too great for passing through the terminal cells..
We arrive then at the condition that when running the difference of potential
maintained at the end of the accumulators must be much greater than the electro-
motive force of the accumulators themselves and further must be equal to the
electromotive force required to make the carbons incandesce. Hence when the
dynamo is, stopped and its circuit broken there would be a sudden falling off in
the electromotive force between the ends of the accumulators that is between the
terminals of the lamps and which would cause the light to seriously diminish. To
avoid this we carry out the following contrivance-When the dynamo is running
and charging the accumulators they are arranged partly in series and partly in
parallel circuit but when the dynamo slows or stops the contrivance which may
be automatic or not which is employed to break its circuit to prevent the accumu-
lators discharging back through the dynamo also puts more of the accumulators
in series and less in parallel circuit than was the case while they were being
charged. Hence we arrange that the difference of electromotive force at the end
of the lamps is. the same whether the dynamo be running or be at rest.
This is the case in which when the engine is running it runs always at about
the same speed. Should great alteration occur in the speed it is not merely necessary

page_text: to have the charging contact makers brought closer together or further apart but
it is necessary by means of a centrifugal governor to govern the distance apart of
the discharging contact makers.
'
It is easy to see that although in describing our automatic regulation as effected
by a centrifugal governor we have only spoken of cells which do not alter in
their numbers connected in parallel yet the method is applicable to automatic
rearrangement according to speed not only of the number in series but in parallel
circuit
;
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said William Edward, Ayrton and John Perry in the Great Seal Patent
Office on the 22nd March 1883.
WILLIAM EDWARD AYRTON, Professor of Technical Physics, Fellow of the Royal
Society, and JOHN PERRY, professor of Mechanical Engineering and Applied
Mathematics in the City and Guilds of London Technical College, Finsbury, in the
County of Middlesex. IMPROVEMENTS IN REGULATING CURRENTS FROM VOLTAIC
CELLS AND TO AND FROM SECONDARY BATTERIES WHEN BEING CHARGED AND
DISCHARGED, AND IN APPARATUS CONNECTED THEREWITH
>
When a variable number of Voltaic Cells, or a variable number of Secondary
Batteries are being charged or discharged it is usual to have the cells arranged
so that the positive pole of one cell and the negative pole of the next are perma-
nently connected together, and the insulated studs of the commutator are
respectively connected with these junctions of positive and negative poles, so that
two moveable contact pieces which are attached to the two ends of any circuit
enable their being placed one on any one of the studs of the commutator, and the
other on any other one of the studs, and so that all the cells existing between these
two studs in question are charged or discharged through the circuit of which we
have spoken. Now as the number of cells is altered by the sliding or rolling of,
one or both of the contact pieces, either the contact piece, leaves one stud com-
pletely before it touches another, in which case the circuit is temporarily broken
and the current interrupted; or else the contact piece before entirely leaving one'
stud touches the next. In this latter case the circuit is not interrupted, but the
cell or. cells which are being added to, or subtracted from, the circuit are
temporarily short-circuited through the contact pieces and are consequently
damaged or at any rate most unnecessarily discharged, and highly injurious sparking
occurs.
•
Now the first part of our Improvement consists in substituting for each of these
single moveable contact pieces a contact-maker consisting of two or more metallic
pieces which together form the contact-maker, and which are connected together
through a resistance coil or coils which may move with them. One only of these

page_text: contact pieces of each contact-maker is connected with one end of the circuit
referred to above, and through which the cells are charged or discharged. When a
contact-maker consists of two contact pieces they are so arranged that when they
are moved together neither of the contact pieces can touch two adjacent studs of the
commutator at the same time, but the front one touches the stud in advance before
the hinder leaves the stud which is being left. Hence, first the circuit is not
broken, and, secondly the cell, or cells, that are being added or subtracted are
not short-circuited; and further--since they are added to the main circuit, first,
through the resistance coil and, secondly, directly, the alteration in the current is
more gradually produced than is the case with the ordinary forms of commutators.
Another plan we adopt is to make both the going and return wire of the circuit
through which the cells are to be charged or discharged double, and in place of
connecting the two moveable contact pieces by a resistance coil as previously
explained we attach the two ends of the going wire respectively to the contact
pieces of one contact maker and the two ends of the return wire respectively to
the contact pieces of another contact-maker, so that when either contact-maker is
moved the cell added or subtracted is not temporarily short-circuited, but is
temporarily allowed to send a current through the whole of the going wire, or
through the whole of the return wire either of which even in the case of a com-
paratively short circuit would have a considerable resistance compared with that
of an accumulator. Hence the current so produced would not be injuriously large.
Thus in figure 1 Aa Bb &c. are voltaic cells or accumulators The positive
pole B and the negative pole a of the preceding cell are permanently connected
with the stud 2. The positive pole C of the 3rd cell and the negative pole b of
the 2nd are permanently connected with the stud 3 and so on. m and n are two
contact pieces attached to the same moving arm but pressing independently on
the studs. m and n are either connected through a moveable resistance coil or
they form the two ends of a cable which is double. Thus we show in figure 2 how
mand n forms two ends of the supply cable and p and q the two ends of the return
cable for a room which is being lighted electrically from the Accumulators or Voltaic
batteries. Again in figure 3 we show m and n the two ends of a double cable
together forming say the positive terminal of the dynamo machine D, p and q
forming the negative terminal. In some cases, whether in charging or discharging,
one lead only has to be moved in order to alter the number of Accumulators or Cells
being charged or discharged. In that case either a double contact-maker with a
resistance coil, as above described, is attached to the moveable lead, or that lead is
made double as previously described; the other lead in each case being permanently
attached to some one of the accumulators. It is obvious that the two contact pieces
forming the contact-maker may be metallic sliding pieces, or metallic rollers, or
rolling metallic brushes something like a common rotating barber's brush in con-
struction, or they may be wheels with metallic projections fitted into concavities
in the studs or into mercury cups. When we use sliding contact-makers, each
contact piece, of which this contact-maker is formed, may be pressed down with an
independent spring which may be a spiral spring or may be a flat spring which
catches a sliding piece by a slot at its end, the sliding piece having a feather so that
there shall be a proper distribution of pressure and no tendency to tilt at one edge.
Thus in figure 4 we see how the sliding piece A is kept making good contact by
means of a spiral spring. Again in figures 6, 7, 8 and 9 we have the curved flat
spring with pins and slots at its end more clearly seen in the perspective drawing in
figure 10 where a feather and slot are employed The studs of the commutator may
be flush with a súrface of wood, or other insulating material, which forms the
strong backing of the Instrument, or the studs may project above the wood, a stop
being attached to each piece of the contact-maker to prevent its sinking much
below the level of the upper surface of the stud when it is between two studs of
the commutator. Thus in figure 8 it will be seen that, whilst each sliding piece is
pressed down by a separate spring, there is a stop which prevents its lowering
more than a certain amount. This is better seen in the diagram figure.11.where

page_text: the spring E is always pressing against the block A. But between two commu-
tator studs should A really move downwards it can only move a very short
distance the part C D coming into contact with the shoulder of B which supports
it. When two or more rows of cells, or accumulators, in series have to be charged
or discharged in parallel circuit the plan we employ consists in connecting the
corresponding cells in each of the rows with consecutive studs of the commutator,
and using a single moveable contact piece which is large enough to touch at the
same time as many studs as there are rows of cells used in parallel circuit. If then
the contact piece be moved on, the additional cell is added to, or subtracted from,
successively each of the rows, and at no time is the circuit broken or the cell short-
circuited. Another advantage possessed by this method is that, although the cells
are charged and discharged in parallel circuit, corresponding cells in the various
rows are not connected together except when they are terminal cells of a series
employed, and even then only when charging or discharging takes place.
This prevents the wasteful discharging of good cells through any others
which, from being partially short-circuited, or from any other cause have a
lower electro-motive force than the remainder. Thus in figure 5 B is an arm
carrying four contact pieces which are all metallically connected together, so that
they form one large contact piece, and in order that the contact shall be good
they are pressed down by independent springs. They touch five studs and the arm is
shown as it really is when a change is being made. If the studs, figures 1, 2, 3, 4, 5
only were touched by the contact piece all the cells shown at X would be in
.circuit. When, however, it is 4, 5, 6, 7 and 8 which are being touched, the cells
1' 2 and 3¹ are no longer in circuit, only cells 4 and 5¹ of the X set are in circuit,
and those cells which are not in circuit are prevented from discharging through one
another, as they probably would otherwise do, on account of very small
differences in their electro-motive forces. In all our commutators we add, when
desired, a locking arrangement for a handle by means of which it is made impossible
to leave a handle in a wrong position with one of the metallic pieces of a contact-
maker resting on one of the fixed studs and the other on the next fixed stud, in
consequence of which a cell would be sending a continuous and unnecessary current
through the resistance coil attached to our commutator, or through the going lead
the two ends of which are in one of our plans attached to the two metallic pieces of
a contact-maker, or through the return lead when the two ends of the latter are
attached to the two pieces of the contact-maker. In one form of our locking
arrangement a small roller is attached to the moving handle and is pressed down
by a spring on a rail formed of a series of hills and hollows the handle having
therefore a strong tendency to rest when the roller is in one of the hollows. In
figure 6 for example the small roller R is attached to the short arm pivoted to the
main handle at P and pressed down by a spring. The rail W on which R runs is
not level but as shown in W W₁, figure 7, consists of a series of hills and hollows
so that the main handle always tends to rest with R in one of the hollows of the
rail. The Second part of our Invention relates to the method of charging and dis-
charging accumulators to enable a constant amount of electrical power to be given
to the lamps, or motors, in spite of variation in the source employed to charge
these accumulators. When any mechanical source of power which varies in its
speed is employed in the driving of a dynamo machine the current from this
dynamo machine being used for the charging of accumulators and working of
lamps & motors-we find it is still possible to give a nearly constant amount of
power to the lamps or motors in spite of variation in the source of power. Our
arrangement is suited to cases in which the direction of motion of the prime mover
may be opposite, or may be varied with any degree of fluctuation, and our arrange-
ment is automatic in its character, but differs in the details depending on the rate
at which the energy is being stored in the accumulators. First-let us take a case
in which the rate at which energy is being stored in the accumulators is not great
in comparison with the rate at which energy is being supplied to the motors or
lamps. This would apply where the time during which the accumulators have alone

page_text: to supply electric energy is small compared with the time during which they are
being charged. In such a case one of our methods consists in fixing the brushes of our
dynamo to a frame which is constrained by springs to place itself near the mean
position, in which position the brushes are arranged so as not to make contact with
the external circuit, and this occurs as long as it is only the friction of the rotating
commutator which is acting; but on this frame we have a cylindric piece P,
figure 12, which is concentric with the spindle of the machine, and there is a
mass M attached to this spindle by means of a spring arranged so that at any
speed of the dynamo machine greater than a certain definite speed this mass
presses outwards by centrifugal force against the inner surface of P and its friction
with P causes two arms A A fastened to the brush frame B B figure 12, of
which another view is shown in figure 13, to move round in the direction of
rotation, so that the brushes now make contact, say, with the terminals F and G
of the external circuit, and at the same time the necessary amount of lead is given
to the brushes at their points of contact with the commutator. Further the greater
the speed the greater the amount of lead given to the brushes because the contact
pieces D E are flexible. When the speed diminishes below a certain amount
the frame carrying the brushes gets nearer the mean position, and there is no
longer contact with the external circuit; and when the direction of motion is
reversed the lead of the brushes is also reversed, and at any speed above a certain
limit contact is established between E and H, and G and D, in the opposite
direction, the lead of the brushes as before increasing with the speed. F and H
form together one terminal of the external circuit, the other terminal being G.
Another plan we employ is to use a "Governor " somewhat like a steam-engine
governor, so arranged that the more the balls fly out the greater is the lead given
to the brushes. Also that the direction of rotation of the Governor by causing a
catch to engage in one or other of two stops causes the lead to be given to the
brushes in the right direction. When the balls fly out less than a certain amount
the brushes are taken off the dynamo commutator so that at all speeds less than
this the dynamo circuit is interrupted. Now the accumulators are supposed to be
arranged as above-mentioned and joined up to the studs of one of our commutators
described in the first part of this specification, and the terminals of the dynamo
machine, see, figure 14, are joined to two contact makers A and B resting on these
studs so that when the dynamo is delivering a current some or all of this current
is used in charging those accumulators whose studslie between these two
contact makers. The lamp or circuit terminates in two other contact makers
C and D which can also slide or roll on the studs or be permanently connected
with certain studs. A and B, for example, may be attached to the ends of two
arms which enable them to receive the required sliding motion. Now we allow
any suitable form of speed-governor to actuate these two arms in such a way that
when the speed of the dynamo diminishes the arms are brought closer together
so that there is a less number of cells being charged and when the speed increases
the arms are separated so that a greater number of cells are being charged. Hence
whatever be the speed of the dynamo it can be so arranged that a current is never
sent back through it by the accumulators. Now it is obvious that if the field-magnets
of the dynamo haves cores which are made partly of cast iron, or of steel, some of the
cells will be charged with electricity at any of the very different speeds at which
we assume that our dynamo can deliver a current. And sometimes to ensure our
obtaining current at any speed from the dynamo machine we keep the field magnets
fed by some or all of the accumulators. Or we may arrange that the terminals of
such a field-magnet circuit enclose between them a variable number of the
accumulators that are being charged. Either by hand, or by means of an automatic
arrangement, the number of these Cells is altered as the speed of the dynamo is
altered so as to give a stronger field at low speeds and a weaker field at high speeds.
With this apparatus we usually combine an arrangement which causes the two
arms to rotate, as if they were fixed together, and such that when the arm reaches
the last stud of a commutator it. pushes against a top-heavy lever which reverses

page_text: the direction of motion, the two arms now moving slowly in the opposite direction
to that in which they moved at first. In this way we effect a partial equalisation
in the charging of the cells at the lower speeds. This apparatus is shown in
figure 15. where the shaft C D gets motion from the engine by means of the
pulley B B, and the Governor-balls F E rotate with this shaft. The spur-
wheels G H and the friction bevel gearing J I give motion to the shaft on which I
is keyed, and from this shaft a belt drives L; the worm-wheel M which is keyed to
the sleeve N getting a slow rotation. S and R are tumbling levers which can be
thrown to one or other side of the vertical by a catch on the worm-wheel, and
these tumbling-levers throw one or other of the friction bevel wheels I into gear
with J by means of the piece K; so that the motion of the shaft. to which I is
keyed, and therefore of the worm-wheel, is continually being reversed. Now the
sleeve N carries with it one arm of the commutator T. T. Q, and the other arm VP is
carried by the inner brass sleeve W which rotates with N, the connection between
W and N. being a pin which passes through a spiral slot. Now when the speed
increases and the Governor balls F. E fly out the sleeve W is drawn downwards,
and because of the spiral feather gives a relative angular motion to W and N
which causes the arm V to get further away from T. Hence the distance apart
of V and T is always greater with greater speeds, and there is a continual motion
over the commutator of both arms which is continually being reversed at the ends
of the commutator by the action of the tumbling-levers. We may also, when
necessary, arrange that the positions of C and D are controlled by means of the
speed-governor. Second-Let us now take a case in which the rate at which
energy is being stored in the accumulators is comparable with the rate at which
energy is being supplied to the Motors or lamps. This applies where the time
during which the accumulators have alone to supply electrical energy is comparable
with the time during which they are being charged, as for example in the case of
electrically lighting the Metropolitan Railway trains in London, or any frequently
stopping trains. Here the source of power being the motion of the railway
carriage, the rotation of the wheels of which turns a dynamo machine on the
train, which when running supplies more than enough electrical energy to light the
lamps, the residue (which in consequence of the times of the stoppage of the train
being nearly. equal to the times of running must be nearly half the total amount of
electrical energy produced by the dynamo) being stored up in the accumulators,
and which residue is employed in keeping the lights burning when the train is going
slowly or stopping. In such a case we find it necessary to effect an electrical
re-arrangement of the accumulators when starting or stopping, the above-mentioned
automatic apparatus being unable to produce even an approximately constant
supply of electricity to the lamps. In this case we may, or may not, employ the
automatic adjustment of the charging handles previously described, but the more
important object which we effect is the automatic re-arrangement of the accumulators.
This will be better understood by taking a simple case- - Suppose that the dynamo
machine when delivering a current is run at a nearly constant speed, then when
the stoppages are as long as when it is running it is clear that the amount given to
the lamps by the dynamo during running must be equal to that given to the
accumulators. Hence the difference of potentials maintained at the terminals of the
accumulators when the dynamo is running inust be greater than the electro-motive
force of the accumulators themselves in order that sufficient charging current may
be sent into the accumulators. On the other hand the difference of potentials at
the two points in the accumulator circuit which are attached to the lamps must be
that suitable for causing the carbons to incandesce. Further these two points
must always be at the end of the accumulators, otherwise a current sent through
the terminal cells and which would have to be sufficient to light the lamps as well
as to charge the remainder, would be far too great for passing through the terminal
cells. We arrive then at the condition that when running the difference of
potentials maintained at the end of the accumulators must be much greater than
the electro-motive force of the accumulators themselves and further-must be equal

page_text: to the electro-motive force required to make the carbons incandesce:
Hence when
the dynamo is stopped and its circuit broken there would be a sudden falling off in
the electro-motive force between the ends of the accumulators, that is between the
terminals of the lamps, and which would cause the light.to seriously diminish.
To avoid this we carry out the following contrivance-When the dynamo is
running and charging the accumulators they are arranged partly in series and
partly in parallel circuit; but when the dynamo slows or stops the contrivance,
which may be automatic or not, which is employed to break its circuit to prevent
the accumulators discharging back through the dynamo puts more of the
accumulators in series and less in parallel circuit than was the case while they were
being charged. Hence we arrange that the difference of potentials at the end of
the lamps is the same whether the dynamo be running or be at rest. To take the
simplest case let G H and EF figure 16 be the leads to the lamps. Let A and B
be the terminals of a number of accumulators in one series, and C and D the
terminals of another set. It is evident that if when G and E cease to be the
terminals of the dynamo machine the automatic, or other mechanism, which effects
this object also breaks the connections CM and BN and joins C and B; the two
sets of cells now form one set in series, and our object is effected. This is the case
in which when the engine is running it runs always at about the same speed.
Should great alteration occur in the speed it is not merely necessary to have the
charging contact-makers brought closer together, or further apart, but it is necessary.
by means of a centrifugal governor to vary the distance apart of the discharging
contact-makers. It is easy to see that although in describing our automatic
regulation as effected by a centrifugal governor we have only spoken of cells which
do not alter in their numbers connected in parallel, yet the method is applicable.to
automatic re-arrangements regulated by the speed, and which vary not only the
number in series but also the number in parallel. And the method last described of
re-arranging the accumulators we also employ when necessary even when the rate of
charging the accumulators is very small compared with the rate of discharging.
Having now described and particularly ascertained the nature of our said Invention
and the manner in which the same is to be performed, or carried out in practice,
we hereby declare that what we consider to be novel, or original, and therefore
claim as the Invention secured to us by the herein before in part recited Letters
Patent is (1) In commutators for charging or discharging variable numbers of
accumulators, or voltaic cells, the use of a contact-maker of two pieces connected
together through a single resistance coil, or placed at the two ends of a double
cable, substantially as described and shown in figures 1, 2 and 3. (2) A
locking arrangement in combination with a commutator to make it impossible
to leave the handle in a wrong position, substantially as described and shown in R
and W in figures 6, 7 and 8. (3) The use of a moveable contact piece of large
size, capable of touching several commutator studs at once, combined with our
method of arrangement for charging and discharging in parallel circuit, two or more
rows of cells or accumulators in series, substantially as described and shown in
figure 5 (4) The moveable brush-holder for a dynamo machine run at different
speeds backwards and forwards giving a lead dependent on the speed, and
a connection with the charging leads of accumulators which ensures the current
being given to the accumulators always in the same direction whatever the direction
of rotation, substantially as described and shown in figs 12 and 13. (5) The
method of varying the number of accumulators being charged by approximating or
separating the charging handles of the commutators by means of a centrifugal
governor, and keeping both handles continually moving over the commutator studs,
substantially as described and shown in fig 15 (6) The use of a stop to
prevent a contact maker falling more than a very short distance when it leaves a
commutator stud, substantially as described and shown in fig 11.
method of causing the automatic, or other arrangement, which disconnects the
dynamo machine from the accumulators and lamps to effectuate an alteration in
the arrangement of the accumulators so that there will be a less number in parallel
(7) Our

page_text: and a greater number in series when working the lamps by themselves, substantially
as described, an example being given in figure 16. In witness whereof we the
said William Edward Ayrton and John Perry have hereunto set our hands and
seals this twenty second day of March in the year of our Lord One thousand
› eight hundred and eighty three
WILLIAM EDWARD AYRTON (L.S.)
JOHN PERRY
(L.S.)