IMPROVEMENTS IN ELECTRIC LIGHTING AND IN APPARATUS CONNECTED PROVISION APPARATUS CONNECTED THEREWITH PARTLY APPLICABLE TO OTHER PURPOSES.
Year: 1882

page_text: LETTERS PATENT to Philip Cardew Lieut. in H. M. Corps of Royal Engineers
and of Brompton Barracks Chatham in the County of Kent, for an Invention
of "IMPROVEMENTS IN ELECTRIC LIGHTING AND IN APPARATUS CONNECTED
PROVISIONAL SPECIFICATION left, by the said Philip Cardew at the Office
of the Commissioners of Patents on the 26th October 1882.
PHILIP CARDEW Lieut: in H. M. Corps of Royal Engineers and of Brompton
Barracks Chatham in the County of Kent "IMPROVEMENTS IN ELECTRIC
LIGHTING AND IN APPARATUS CONNECTED THEREWITH PARTLY APPLICABLE TO
OTHER PURPOSES.'
"
This Invention has for its object Improvements in Electric Lighting and in
Apparatus connected therewith.
The first part has reference to the means of producing measuring and regulating the
supply of the Electricity and consists of improvements in the winding and arrange-
ment of the magnetizing coils of dynamo imachine by means of which it will be
possible to connect any number of arc lamps in what is known as divided circuit or
multiple are without one lamp interfering with the burning of another, and also
when burning incandescent lamp of an improved means of insuring the right
amount of current in every lamp whatever its distance from the Machine
To effect this I take a dynamo machine of any size, say one calculated to give
80 Ampères of current and having a revolving armature wound to a suitably low
resistance. In such a machine the magnetizing coils would usually be of very large
wire capable of carrying this current without overheating. In place of this I wind
these coils with several say 8 different wires capable of carrying '/h of the total
current or 10 Ampères. These several wires may be each partly wound on each
bobbin of the coils or the bobbins may be wound with these wires in any other con-
venient way, care being taken that the magnetizing effect of each wire is in the
proper direction. One end of each of these coils is connected to one of the brushes
of the machine and the other end of each is brought to one of a row of eight
terminals.

page_text: Thus the current divides from the brush and can be taken from the terminals to
as many lamps, the other poles of which are joined to a large lead common to all
and leading back to the other brush of the machine.
The reason of this device is to avoid the short circuiting of the other lamps when
one happens to burn with a very short are or to require to cause the carbons to
touch. By this arrangement when this happens the resistance of the magnetizing
coil and lead is still in circuit, and the increase of current in this circuit increases
the magnetic field for all.
Of course the machine may be so wound that several lamps may be put in series
on each circuit.
In place of the machine being used with 8 lamps each having a current of 10 am:
the terminals might if larger lamps were required be connected in pairs and 4
lamps each having 20 am: be used, or again, 2 lamps of 40 am:, or 1 lamp of 80
am: None of these combinations affecting the current through any part of the
machine or its E.M.F. or speed.
When burning incandescent lights since their resistance is invariable the same
difficulty is not encountered in the multiple are arrangement and for this purpose
all the positive terminals would be connected together and to one large lead,
another large lead issuing from the negative terminal and the lamps being connected
across in multiple arc as required.
With this system of lighting it is very essential that an exact difference of
potential should be maintained in the machine, when supplying any given number
of lamps.
To effect this I use a varying shunt by which the magnetizing coils can be short
circuited, this shunt I form by introducing a piece of German Silver or brass or
other metallic wire between the brush and the terminals before mentioned.
Theoretically to obtain the full power of the machine this wire should have an
infinite resistance. Practically with most large machines a length of 10 feet is
sufficient.
The length of this wire in circuit is varied at pleasure.
When the length is very short the magnetizing coils are practically short
circuited, consequently no magnetism is produced and no current and no difference
of potential at the poles. As the length increases, so does the magnetisin and
current.
In order to vary the length, I fasten one end of the wire to a wooden support
about 6 feet from the ground, the other end is wound round or fastened to a metal
. pulley fastened to the same support and near the other end of the wire, between
these two the wire is allowed to hang in a loop, and kept stretched by a small
weight and pulley. The pulley can be turned by hand so as to vary the length of
the loop of wire. A stiff spring presses against the pulley to prevent it turning,
except when wished and also to give good contact. Leads from the brush and
terminals are connected to this spring, and to the point where the wire is made.
In connection with these terminals is a small switch of the ordinary form by
which the magnetizing coils can be absolutely short circuited at once, and all
current cut off.
The attendant at starting takes care that the wire of the shunt is nearly all
wound up, so that there will be very little current. When the engine has attained
its proper speed he gradually unwinds the wire, thus increasing the current until
he observes by means of a potentio-meter or Vultmeter that the proper difference
of potential is obtained at the machine.
At any time should the difference of potential be observed to be too great or too
small from alteration of speed or other causes he can regulate it by altering the
length of the shunt wire. Also if at any time fewer lamps are burning, which will
be observed by the current being lessened he can lower the Potential to the required
amount since with less current a less amount of the total Potential will be absorbed
'in the leads.
When however the attention of the person in charge cannot be continuously kept

page_text: on the indications of the Voltmeter I employ a form of apparatus which will
automatically maintain the difference of potential constant
This Automatic Regulator consists of 2 small rails of nickel plated steel or
other metal on which runs a small electromotor or machine in which an armature
is caused to rotate by a current of electricity passing through coils of wire the
rails are laid parallel to each other at the proper distance apart on a plank of wood
or other suitable non conducting material and flanged wheels on the axle of the
electromotor run on the rails
The rails form the resistance to shunt the magnetising coils of the dynamo
machine and perform the same function as the loop of wire described above the
circuit being completed through the wheels and axle of the electromotor The
Electromotor is wound to a high resistance say 1000 ohms-One end of its coils
which are partly magnetising and partly rotating as in a dynamo machine, is con-
nected to the body and axle of the motor and thus to the rails and magnetising
coils of the dynamo and the brush in connection with them, the other end is
connected to the other brush by means of a third small wheel insulated from the
body of the motor and running on a third insulated rail centrally disposed between
the others. Thus the coils of the motor form a high resistance shunt on the poles
of the dynamo and the current through them depends on the difference of Potential
existing between these poles. The ends of the small railway are closed by proper
buffers to prevent the motor running off at either end-The plank carrying the
railway is laid on a level floor and the connections from the rails to the brush and
terminals before mentioned properly made at one end of the railway which is then
tilted up by means of a screw to a height depending on the difference of Potential
to be maintained-Thus the railway forms an inclined plane The motor is put at
the upper end of this and secured until the machine is started, the motor is then
released and commences to travel down the plane under the action of the resolved
part of its weight. As it does so it increases the resistance of the shunt on the
magnetising coils of the dynamo, consequently the difference of Potential between
the poles of the dynamo is increased and therefore the current through the coils of
the small motor. This current is so directed through these coils as to tend to
cause the motor to travel up hill and therefore it gradually stops in such a position
as to maintain the right difference of Potential between the poles of the dynamo.
Any alteration in this is at once felt by the motor which takes up a new position
either further up or lower down, the constant force of its weight acting down hill
requiring to be balanced by a constant force tending to drive it up hill
This Automatic Regulator can also be used with dynamo machines in which the
magnetising coils are arranged in a shunt circuit
In this type of machine the strength of Field is regulated by interposing more
or less resistance in the circuit of the magnetising coils and the more resistance
interposed the weaker becomes the Field
The resistance in this case will be that given by the rails up to the motor the
current being brought in at the bottom of the inclined plane
By means of this Automatic Regulator the difference of Potential the poles of
the Generator can be kept exactly constant at the required number of Volts but
this difference should be altered slightly for every considerable alteration of current
which will vary according to the number of lamps alight. Thus if the lamps
require a difference of Potential of 50 Volts, when they are all alight that at the
Generator may require to be Sixty Volts or even greater but when there are only a
few lamps alight probably about 54 V would suffice
In order to provide for this the screw which elevates the Railway must be altered
from time to time to suit the variations of current in accordance with a table
provided calculated from the known conductivity of the leads to give the correct
difference of Potential at the extreme end of the system
Even with this arrangement when one machine supplies lamps at considerably
varying distances from one pair of main leads the lamps nearest the machine will
have more than the proper number of Volts supplied to them
.

page_text: To obviate this when the derived circuit contains few lamps I interpose in this
derived circuit a fixed resistance sufficient to insure the safe number of volts to the
lamps not being exceeded but when a derived circuit containing a considerable
number of lamps is taken off I interpose in the circuit an Automatic Regulator of the
same form except that four insulated rails are employed to enable the difference of
Potential which drives the motor to be exactly that supplied to the lamps
Any form of current measurer may be used but I also employ a new form con-
sisting of a similar small motor but wound with a few turns of thick wire through
which the main current or a definite part of it is sent by means of the two rails
and wheels which are insulated from each other
The rails instead of being laid on a flat plank are laid so as to gradually incline
upwards in a circular curve from the horizontal line at which they start cut out
of a piece of wood or several pieces built up or the bed for the rails may be
constructed of cement or other suitable substance
The rails and wheels in this case are more massive so as not to oppose needless
resistance in the circuit. When the current is passing the motor will be urged
forward to a certain distance up the incline stopping at the point where the incline
becomes so steep that the weight of the motor balances the force of the current.
The current varies according to the square root of the horizontal distance from the
starting point where the rails are horizontal
When it is required to measure the amount of electrical energy being produced
in the circuit a similar motor is employed except that, while the magnetizing coils
of the motor are wound with thick wire to take the main current the revolving
coil is wound to a high resistance and is connected as a shunt on the circuit as in
the case of the automatic Regulator The force acting on this motor will then be
proportional to the current multiplied by the difference of Potential or the energy
in the circuit
This motor can be put on the same rails as the current measurer and the energy
will be proportional to the horizontal distance from the starting point
In all cases where these motors and rails are employed whether for regulating or
mensuring switches are provided to short circuit the rails when desired--
In all cases also the movements of the motors can be made self recording by
means of pencil points on the motors tracing curves on cylinders covered with
paper rotated by clockwork or in any other convenient way, and the current and
energy meters may be used to measure and record the amount of current or
energy supplied to any part of the circuit and thus become meters by which the
charges are assessed
The meters as above described for use with incandescent lamps can also be used
with are lamps or generally to measure and record the amount of current and
energy supplied for any purpose
My improvements in Electric lamps have reference especially to the means for
separating and regulating the distance of the carbons in are lamps
For this purpose when several lamps are burnt in series I employ a lamp in
which the regulation is effected by the varying magnetism in an electro magnet
varying the rate of vibration of a piece of soft iron vibrating under the influence
of this magnetism
The positive carbon is attached to a heavy rack which is geared to the driving
wheel of a small clock from which the spring has been removed. On the escape-
ment of this clock in place of the pendulum or balance wheel is a small piece of
soft iron of suitable shape pivotted through its centre of gravity. Just above this
piece of iron is the pole of an electro magnet wound to a resistance of about
1000 Ohms, outside this coil are a few turns of thick wire. The fine wire is con-
nected to the two terminals of the lamp so as to be a shunt on the are The thick
wire is made to form part of the main circuit and the currents through these
two coils are made to oppose each other in magnetizing effect, that through the fine
coil considerably predominating. To regulate the motion the magnet can be
moved further from or nearer to the vibrating piece of iron

page_text: The carbons are separated to start the arc by means of a magnet at the end of
the rack lifting the positive carbon holder through a short distance
When the arc is established the regulating magnet is excited, the piece of soft
iron begins to vibrate and the rack with the positive carbon to slowly descend
If the rate of descent is not sufficient so that the are becomes too long the
magnetism is increased and the vibrating piece moves quicker-If the arc gets too
short it moves slower-In order that the vibrating piece may be stopped at the
end of its stroke when the current ceases a small bent lever attached to a piece of
iron over the other pole of the regulating magnet is so pivotted and arranged that
when there is no current it pushes the vibrating piece to the end of its stroke but
when the current starts the piece of iron is pulled down and the lever releases the
vibrating piece
Should the arc at any time go out from bad regulation or other cause the
magnet at the end of the rack releases the positive carbon holder which at once
drops and contact is restored
It will be understood that the weight of the rack &° actuates the clock work
in place of the ordinary spring
.
When however all the lamps are in divided circuit or for large lamps in which
the arc requires to be rapidly lengthened or shortened to maintain it burning
regularly and well I adopt the following form a lamp The positive Carbon is fed
by means of a rack gearing in a pinion on the axle of which is a large toothed
wheel. This wheel is made to gear into a pinion on the axle of which is a spur
wheel this spur wheel is prevented. from turning which it tends to do under the
influence of the weight of the carbon holder &c. by a steel detent at the end of a
spring on which is the armature of the magnet. When however this magnet is
excited by a current the spur wheel is released and the carbon begins to descend.
Immediately however that the detent has cleared the spur wheel it makes a contact
which short circuits the magnet coils. The armature then springs back and catches
the next tooth of the spur wheel. Should the current still be passing through the
magnet the operation is then repeated so that the positive carbon descends
slowly
The negative carbon holder is brought up above the arc by two uprights united
to a yoke at top and bottom in the usual way from the centre of the yoke above
the arc springs a short rack about 3 inches long geared into similar wheels to those
of the positive carbon holder and with a similar magnet to operate it working in
the same way
The negative rack is behind the positive one and the arms are inclined so as to
bring the carbons in line.
The Regulator is essentially a Galvanometer Bobbin with a needle pivoted in the
centre of the Bobbin and made to hang vertical by preponderance
The bobbin is wound with two coils one consisting of a few turns of very thick
wire.forming part of the main circuit and the other of a fine wire coil of about
1000 ohms resistance The thick wire coil is on the positive side of the lamp one
end is connected to the brass bobbin
The needle has an index of brass whose end projects slightly beyond the bobbin
as shewn and is tipped with Platinum. It hangs between two platinized screws so
that when the needle moves to one side or the other the pointer makes contact
with either one or other of the screws
The needle is in connection with the bobbin by its pivots but in addition a light
spring fastened to the bobbin presses against a very small disc of metal on the axle
of the needle so as to avoid the passage of the current through the pivots but so as
not to oppose much resistance to the movement of the needle
The screws work in brass pieces insulated from the bobbin. The inner end of
the fine coil is brought out to an insulated terminal by means of which it is
connected to the negative side of the lamp 900 ohms are then wound on and the
wire then connected to an insulated terminal by means of which it is placed in
connection with one end of each of the small magnets that work the lamp the

page_text: other ends of these magnets are connected to screws 100 ohms more wire are then
wound on the bobbin and the end finally connected to the brass bobbin Thus
when contact is made by the pointer with either of the screw contacts one or other
of the small magnets is excited by half the current flowing through the fine wire
the other half continuing to pass through the first 100 ohms of the bobbin. Care
must be taken that the main current passing through the thick wire tends to force
the needle to make contact with the magnet working the lower carbon holder and
thus increase the length of the arc, that flowing through the shunt coil on the
contrary should tend to make the needle make contact with the other magnet and
thus diminish the arc-This regulator with its magnets should therefore always
keep the are of a constant length As the current is tapped from the outer windings
of the coil on the bobbin the effect of tapping part of the current from them will
hardly be felt on the suspended needle especially as the current flowing through
the rest of the coil is thereby increased. The Regulator may either form part of
the lamp or may be separate so as to be placed in a convenient position below the
lamp where its working may be watched. If this disposition be adopted in order
to avoid having more extra leads to the lamp than necessary the needle may be
-insulated-from-the-brass part of the-bobbin and connected-to the intermediate point
of the fine wire coil two leads to the magnets one from each screw contact point
will then be all that is requisite the other ends of the magnets being connected to
the positive side of lamp of course these leads may be very sinall.
The bobbin is regulated for different currents by shunting the thick wire coil
more-or-less-by-a-small-piece-of-bare-wire-clipped-between-the-terminals-at-the-
ends of the coil

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Philip Cardew in the Great Seal Patent Office on the 26th April
1883.
PHILIP CARDEW Lieut: in H. M. Corps of Royal Engineers and of Brompton
Barracks Chatham in the County of Kent "IMPROVEMENTS IN ELECTRIC LIGHTING
AND IN APPARATUS CONNECTED THEREWITH PARTLY APPLICABLE
PURPOSES"
TO OTHER
This invention has for its object improvements in electric lighting and in
apparatus connected therewith.
The first part has reference to the means of producing the electricity and consists
of improvements in the winding and arrangement of the magnetizing coils of
dynamo machines by means of which it will be possible to connect any number of
arc lamps in what is known as divided circuit or multiple arc without one lamp
interfering with the burning of another or to use incandescent and are lamps on
the same machine without any interference or to use a number of circuits for
other purposes without interference of one circuit with the other.
To effect this I take a dynamo machine of any size say one calculated to give
80 amperes of current and having a revolving armature wound to a suitably low
resistance. In such a machine the magnetizing coils would usually be of very
large wire capable of carrying this current without overheating. In place of this
I wind these coils with several say eight different wires capable of carrying 1/8th
of the total current or 10 amperes. These several wires may be each partly wound
on each bobbin of the coils or the bobbins may be wound with these wires in any
other convenient way care being taken that the magnetizing effect of each wire
is in the proper direction. One end of each of these coils is connected to one of
the brushes of the machine or to a plate in connection with this brush and the
other end of each is brought to one of a row of eight terminals.
Thus the current divides from the brush and can be taken from the terminals to
as many lamps, the other poles of which are joined to a large lead common to all
and leading back to the other brush of machine.
Figure 1 of the drawings hereunto annexed shews a diagram view of one form
of Gramme machine wound for eight circuits as above described. In this figure
A is the positive brush of the commutator. B is the negative brush. C is an
insulated brass plate with connections to positive brush and to eight magnetizing
coils indicated by the dotted lines G. D is a wooden board with eight positive
terminals and one negative terminal with connection to negative brush. È is the
armature axis and F are the magnet poles.
The reason for the above described device is :-
1. To avoid the short circuiting of the other lamps when one happens to burn
with a very short are or to require to cause the carbons to touch.
By this arrangement when this happens the resistance of the magnetizing coil
and lead is still in circuit and the increase of current in the circuit the magnetic
field of the machine so that there is no perceptible change of current in the other
lamps.
2. To enable a considerable number of the lamps to be extinguished at any time
by simply breaking their circuits without any interference with the lamps that are
left burning, since every lamp put out weakens the magnetic field proportionately
by the cessation of current through the magnetizing coil belonging to it.
In fact by this arrangement the lamps are quite independent of each other.
3. To obtain the best possible effect from differentially wound lamps that is to

page_text: ;
say lamps in which the regulation is effected by opposing the magnetizing action
of a coil of thick wire through which the main current passes to that of a coil of
fine wire connected as a shunt to the arc so that the current passing through it is
due to the difference of potential existing between the two carbons at the time.
To illustrate this each of the diagrams 1. 2 and 3 represent a machine for four
lamps. Diagram 1 is arranged to burn the lamps in the simple multiple are
assuming that lamps can be made to burn with this connection.-Diagram 2 to
burn the lamps in the ordinary series method.-Diagram 3 to burn them according
to my system of multiple arc.
The machine would be the same in each case except that in Diagram 2 the
armature would have to be wound with thinner wire to produce the necessary
difference of potential at tho brushes and the magnetizing coils would be connected
in series instead of in multiple arc.
-
In each A is the commutator, B the positive and C the negative brushes D the.
lamps.
The figures shew the difference of potential that would be found in each case,
between the brushes, between the ends of the magnetizing coils and between the
carbons of the lamps when burning well, assuming for the sake of simplicity that
the lamps are so close to the machine that the loss of potential in the leads may
be disregarded.
The machine is in each case doing exactly the same work.
Now it will be evident to any one acquainted with the laws of electricity that
assuming the difference of potential between the brushes to be kept constant a.
shortening of the are in any lamp in Diagram 1 will increase the current through
that lamp but will have very little effect on the difference of potential and any
effect produced on this will be equally felt on the others and tend to derange then.
Lamps therefore to work according to this system should be regulated entirely by
the main current. In Diagram 2 any shortening of the arc in any lamp will
diminish the difference of potential between the carbons of that lamp but will have
very little effect on the current and any effect produced on this will be equally
felt by the others and tend to derange them. Lamps therefore to work according
to this system should be regulated entirely by the difference of potential. In
Diagram 3 any shortening of the are in any lamp will increase the current in that
lamp and at the same time diminish the difference of potential considerably since
more of the available electro motive force will be taken up in passing the larger
current through the magnetizing coil while the other lamps will be quite unaffected.
Hence a differentially wound lamp will work well on this system. If the effect of
a very long arc in one lamp be considered it will be seen to be altogether analogous
in the three cases.
Another advantage possessed by this method of connection is that incandescent
lamps may be fed from some of the circuits and arc lamps from others and the
incandescent lamps will be quite unaffected by the arc lamps.
When the system is applied to street lamps it will be most economical to use
bare suspended wires and insulators on the lamp posts the return wire being
buried in contact with the earth. This can be done with perfect safety and
convenience on account of the low potential used. In place of the machine being
used with a large number of lamps fewer and more powerful Jumps may be used
by connecting the terminals together.
Thus with an 8 lamp machine if the 8 terminals are connected together in pairs
and 4 leads taken, one from each of these pairs, the result will be 4 lamps each
having twice the current supplied to the smaller lamps and giving as is well known
more than twice the light.
Or again the machine may be connected for two circuits giving two lamps or
one giving one lamp. These alterations will not alter the current through any
part of the machine or its electro motive force or speed but the total quantity of
light produced will be greater as the number of lamps is reduced although of course
for most purposes not so well distributed.

page_text: In this system I do not limit myself to the use of only one lamp in each circuit,
or to a machine with only two brushes and two poles but these are the simplest
arrangements.
The second part of the invention has reference especially to the means for,
separating and regulating the distance of the carbons in are lamps.
For this purpose I employ a lamp in which the regulation is effected by the
varying magnetism in an electro magnet varying the rate of vibration of a piece
of soft iron vibrating under the influence of this magnetism.
The positive carbon is attached to a heavy rack which, is geared to the driving
wheel of a small clock with a dead beat escapement from which the spring has
been removed. On the escapement of this clock in place of the pendulum or
balance wheel is a small piece of soft iron of suitable shape pivoted through its
centre of gravity. Just above this piece of iron is the pole of an electro-magnet
wound to a resistance of about 1000 ohms; outside this coil are a few turns of
thick wire. The fine wire is connected to the two terminals of the lamp so as to
be a shunt on the arc. The thick wire is made to form part of the main circuit
and the currents through these two coils are made to oppose each other in
magnetizing effect that through the fine coil considerably predominating.
To regulate the motion the maguet can be moved further from or nearer to the
vibrating piece of iron.
The carbons are separated to start the arc by means of a magnet at the end of
the rack lifting the positive carbon holder through a short distance.
This magnet is actuated by the main current.
When the arc is established the regulating magnet is excited, the piece of soft
iron begins to vibrate and the rack with the positive carbon to slowly descend.
If the rate of descent is not sufficient so that the are becomes too long the
magnetism is increased since a stronger current is sent through the fine wire
coil and the vibrating piece moves quicker. If the are gets too short it moves
slower.
It will be understood that the weight of the rack &c actuates the clockwork in
place of the ordinary spring.
If by any accident the lamp is extinguished the armature of the are striking
magnet is at one released and the positive carbon holder drops through a certain
distance. If the lamp is one of a number connected in multiple are on my system
the vibrating armature will at the same time be working very quickly and from
the combination of the two movements contact is at once restored, but if the lamp
be one of a number connected in series a cut out of the ordinary description will
be necessary to prevent the other lamps being extinguished. This will interpose
an equivalent resistance to the arc in the circuit and cause the vibrating armature
to work and establish contact. If one lamp is required to be extinguished before
the others this can be effected by breaking the circuit of that lamp if they are in
multiple arc, or by short circuiting it if they are in series and in either case this
will have the effect of stopping the clock work and keeping the carbons apart.
The clock work may be entirely enclosed in an air-tight box the main arbor coming
out through a stuffing box and being geared to the rack and pinion by a detent
as in a clock to allow the rack to be raised independently of the clockwork. The
pawl may be released by hand when necessary to allow of free motion in either
direction for the rack when adjusting new carbons or instead of this arrangement
the rack may be pushed out of gear with the pinion against a spring which tends
to bring it back into gear.
The magnet controlling the clockwork and its adjusting screw may be outside
the case containing the clockwork, the vibrating armature being inside. In order
to see that the armature is working properly a piece of stout glass may be inserted
in one side of the case to show the works.
Working drawings of a lamp constructed as above described are shewn at
Figures 2. 3 and 4.
Figure 2 is a front elevation, Figure 3 a side elevation and Figure 4 a plan in

page_text: section of an arc lamp constructed as above described. Figure 5 is a plan view of
the bottoni plate of the frame of the lamp.
In these Figures A, B are the two terminals of the lamp. C is an electro magnet
capable of being raised or lowered by a screw C¹. The magnet is wound with coils
of fine wire the ends of which are coupled to the terminals A B so as to form a
shunt on the arc. Outside the fine wire coils are a few turns of thick wire forming
part of main circuit. D is the vibrating piece of soft iron pivotted through its
centre of gravity. D' is a dead beat escapement on the axis of the piece of iron.
E is the escapement wheel geared by a train of wheels to the axis F on which is
fixed a ratchet wheel G-loose on the axis F is also a pinion H and disc carrying
a pawl I to engage with the teeth of the ratchet wheel. J is a rack gearing with
the pinion H. The rack is vertical and its own weight tends to carry it downwards
and in its descent to revolve the train of wheels. K is an electro-magnet carried
by the lower end of the rack. L is a soft iron armature carrying the positive
carbon holder M. K' are lugs which limit the distance that the armature can drop
away from the magnet. N is the negative carbon carried by the bottom plate of
the frame. O is a glass shade. The course of the main current from one terminal
to the other is indicated by a dotted line of long and short dots-the shunt circuit
is indicated by a dotted line of short dots. Wherever insulating material is used
for insulating one portion of the lamp from another it is marked with broad section
lining in Figure 2.
Having thus described the nature of my invention and the manner of performing
the same I would-have-it understood that I claim as my improvements in electric
lighting and in apparatus connected therewith partly applicable to other
purposes:-
First In dynamo electric machines in which the main current is conveyed
through the magnetizing coils I claim forming these coils of a number of insulated
conductors each connected at one end to one of the armature brushes whilst
_the other ends of the several conductors-are-coupled to separate insulated
terminals to each of which a separate line wire may be connected substantially
as described.
Second. Regulating the distance of the carbons in electric arc lamps by the
varying magnetism of an electro magnet excited by opposing currents, one the
main current and the other of a shunt from it causing a variation of the rate
of vibration of a piece of soft iron pivotted through its centre of gravity and
vibrating in the magnetic field formed by the inagnet substantially as described.
Third. The construction of electric arc lamps substantially in the manner herein
before described and illustrated in the drawing annexed.
In witness whereof I the said Philip Cardew have hereunto set my hand
and seal this 25th day of April in the year of our Lord One thousand eight
bundred and eighty three.