An Improved Rotary Electrical Differential Controlling Device.
Year: 1894

page_text: Date of Application, 29th Mar., 1894
Complete Specification Left, 25th Jan., 185-Accepted, 23rd Mar., 1895
PROVISIONAL SPECIFICATION.
An Improved Rotary Electrical Differential Controlling Device.
ALFRED LYSTER SHEPARD of 8 West Kensington Gardens in the County
of Middlesex Electrical Engineer do hereby declare the nature of this invention
to be as follows:-
My invention relates to improvements in rotary electrical differential controlling
devises and is useful generally for controlling and regulating currents flowing in
electric circuits and more especially for controlling and regulating the current
flowing in an electric arc lamp.
In the following paragraphs I have described how my invention may be adapted
for controlling an electric arc lamp. In carrying my invention into practice for
this purpose I preferably provide an electric motor or, motors having a common
field and two separate armatures, and having for convenience in working two sets
of pole-pieces one for each armature, the spindles of the said armatures are arranged
to run in line with each other, the adjacent extremities being rigidly connected to
the two outer toothed wheels of a set of differential gear, the centre wheel of which
has its axis at right angles to the axes of the armatures, and is arranged to revolve
freely within a cylindrical frame or carrier the axis of which coincides with the
axes of the armatures, the said cylindrical frame or carrier has formed on its outer
periphery a worm or thread adapted to engage with a worm wheel having teeth of
a suitable pitch, the worm wheel is keyed on to a screwed shaft which communicates
the motion of the worm and wheel to the carbon-holders, the field magnets of the
motor are wound with two circuits, one composed of thick wire in series with the
arc and the other of thin wire in shunt on the are, so as always to provide a suffi-
ciently powerful field for the armatures whether the current is turned on to the
lamp with the carbons apart or together. The armatures are wound one with thick
wire and one with fine wire and are coupled as shunts on the main and shunt
windings of the fields respectively.
The winding of the two armatures is so arranged and proportioned that when
the normal current is passing through the lamp the two armatures run at practically
the same speed but in opposite directions so that the cylindrical carrier or frame
carrying the centre wheel of the differential gear remains stationary.; should the
current, however, flowing in the lamp vary from the normal, the two arinatures
will no longer revolve at the same speed, and the carrier or frame will in conse-
quence be rotated in one or the other direction and so move the carbons apart or
together in accordance with the requirements of the lamp; it will be seen from the
above that although the currents flowing round the field magnets vary in intensity,
yet as the armatures are revolving in a common field, the relative difference in
speed of the armatures is controlled by the armature currents alone.
If it is desired to alter the normal working conditions of the lamp, this can be
effected by permanently increasing or reducing the current strength in one or the
other armature, according as the potential or current in the lamp is to be increased
or diminished, either by inserting or cutting out resistances in series with or in
parallel to the armatures or in any well-known way.
In utilizing my invention for the purpose of regulating an electric arc lamp and
more especially an arc lamp intended to be used in conjunction with a reflecting
mirror, or other device for collecting and concentrating the rays of light, I find it

page_text: advantageous instead of having the axes of the two carbons parallel, as is usually
the case, to incline one carbon towards the other with the object of allowing an
uninterrupted passage for the light. I find that when a parabolic mirror is used,
the best results are obtained when the positive carbon is arranged longitudinally
in the focus of the mirror in a direction parallel to the reflected rays, the negative
carbon being fixed at an angle of about forty-five degrees to the positive and
arranged to be fed upwards either by a spring or by the same mechanism which
operates the positive carbon or by any suitable means, the point of the negative
carbon is held in position by a suitable cap or collar formed with projecting
pins or teeth, of some refractory material such as platinum, so as to constantly
maintain the point of the negative carbon in the same place, the said cap or collar
is fixed to a metal tube or guide in which the carbon is free to move vertically, the
tube or guide has formed on its outer surface metal projections or wings for the
purpose of radiating the heat. In order to maintain the luminous crater in the best
position relatively to the mirror, I employ a magnet in close proximity to the arc,
which, by its action, prevents the crater from being formed elsewhere than the
proper place.
Although I have above described how my invention can be carried into practice
for controlling the current in an electric arc lamp, with slight modifications it can
be utilized for controlling and regulating electric circuits generally, for instance in
a system of electric distribution such as the three-wire system it is advantageous
to maintain the pressure on either side of the system the same, this can be effected
by winding the motor fields with wires in which flows a portion of the current
flowing into the positive and negative circuits to be controlled, so as to have a
common field for the two armatures which are preferably shunted on the field
windings, one on the positive and one on the negative side, and are so wound that
when the pressure on the two sides of the system is balanced so as to obtain the
best results, they revolve at the same speed but in opposite directions; the carrier
of the centre wheel of the differential gear, to which the armatures are geared in a
similar manner to that employed in the case of the arc lamp, is adapted to operate
switches, resistances, valves or other controlling apparatus suitable to the source of
power from which the currents of electricity are obtained, any alteration in the
balance between the two sides of the system will cause the two armatures to run at
different speeds thereby moving the centre wheel carrier in such a direction as to
readjust the balance of the circuits by means of the before-mentioned switches,
valves, etc.
In another modification of my invention, I apply my improved regulator to
synchronizing motors, worked either by steam, electricity, fluid pressure, or other
motive power; in this case I can either maintain the speed of the motor to be con-
trolled constant as compared with a machine or apparatus revolving at a standard
speed, or I can ensure a uniform speed or a uniform difference in speed between two
motors. In the first case I cause the standard speed required to be communicated to
one of the two outer wheels of the differential gear, the other wheel being driven by
the motor to be governed, the carrier of the centre wheel is caused to act, either
directly or through the medium of an electric relay operating a motor, on switches,
resistances, valves, or other controlling apparatus, suitable to the special form of
motor to be controlled. In the second case the two motors to be synchronized are
connected in any suitable manner to the two outside wheels of the differential gear,
the carrier of the centre wheel is then adapted to operate either directly or through
the medium of a suitable relay, the controlling apparatus suitable to the special
form of motors as before. Although I have hereinbefore described how my inven-
tion may be conveniently and advantageously carried into practice, it is obvious
that I can somewhat modify the construction for different purposes of my apparatus,
without departing in any way from the nature of my said invention.
Dated this 29th day of March Eighteen hundred and vinety-four

page_text: An Improved Rotary Electrical Differential Controlling Device.
1 ALFRED LYSTER SHEPARD of 8 West Kensington Gardens, in the County
of Middlesex Electrical Engineer 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 :-
My invention relates to improvements in rotary electrical differential controlling
devices and is useful generally for controlling and regulating currents flowing in
electric circuits or conductors and more especially for controlling and regulating
the current flowing in an electric arc lamp.
In the following paragraphs I have described how my invention may be adapted
for controlling an electric arc lamp. In carrying my invention into practice for
this purpose I preferably provide an electric motor or motors having a common
field and two separate armatures, and having for convenience in working two sets
of pole pieces one for cach armature, the spindles of the said armatures are
arranged to run in line with each other, the adjacent extremities being rigidly
connected to the two outer toothed wheels of a set of differential gear, the centre
wheel of which has its axis at right angles to the axes of the armatures, and is
arranged to revolve freely within a cylindrical frame or carrier the axis of which
coincides with the axes of the armatures, the said cylindrical frame or carrier has
formed on its outer periphery a worm or thread adapted to engage with a worm
wheel having teeth of a suitable pitch, the worm wheel is keyed on to a screwed
shaft which communicates the motion of the worm and wheel to the carbon-holders
in a similar manner to that described in my Patent No. 12,439 of 1890, the field
magnets of the motor are wound with two circuits, one composed of thick wire in
series with the arc and the other of thin wire in shunt on the arc, so as always to
provide a sufficiently powerful field for the armatures whether the current is turned
on to the lamp with the carbons apart or together. The armatures are wound one
with thick wire and one with fine wire and are coupled as shunts on the main and
shunt windings of the fields respectively.
The winding of the two armatures is so arranged and proportioned that when
the normal current is passing through the lamp the two armatures run at practically
the same speed but in opposite directions so that the cylindrical carrier or frame
carrying the centre wheel of the differential gear remains stationary; should the
current, however, flowing in the lamp vary from the normal, the two armatures
will no longer revolve at the same speed, and the carrier or frame will in con-
sequence be rotated in one or the other direction and so move the carbons apart or
together in accordance with the requirements of the lamp; it will be seen from
the above that although the currents flowing round the field magnets vary in
intensity, yet as the armatures are revolving in a common field the relative
difference in speed of the armatures is controlled by the armature currents alone.
If it is desired to alter the normal working conditions of the lamp this can be
effected by permanently increasing or reducing the current strength in one or the
other armature, according as the potential or current in the lamp is to be increased
or diminished, either by inserting or cutting out resistances in series with or in
parallel to the armatures or in any well-known way.
In utilizing my invention for the purpose of regulating an electric arc lamp and
more especially an arc lamp intended to be used in conjunction with a reflecting
mirror, or other device for collecting and concentrating the rays of light, I find it
advantageous instead of having the axes of the two carbons parallel, as is usually
the case, to incline one carbon towards the other with the object of allowing an
uninterrupted passage for the light, I find that when a parabolic mirror is used,

page_text: the best results are obtained when the positive carbon is arranged longitudinally in
the focus of the mirror in a direction parallel to the reflected rays, the negative
carbon being fixed at an angle of about forty-five degrees to the positive and
arranged to be fed upwards either by a spring or by the same mechanism which
operates the positive carbon or by any suitable means, the point of the negative
carbon is held in position by a suitable cap or collar formed with projecting pins
or teeth of some refractory material such as platinum, so as to constantly maintain
the point of the negative carbon in the same place, the said cap or collar is fixed to
a metal tube or guide in which the carbon is free to move vertically, the tube or
guide has formed on its outer surface metal projections or wings for the purpose of
radiating the heat. In order to maintain the luminous crater in the best position
relatively to the mirror,-1 employ a magnet in close proximity to the arc, which
by its action prevents the crater from being formed elsewhere than the proper
place.
Although I have above described how my invention can be carried into practice
for controlling the current in an electric are lamp, with slight modifications it can
be utilized for controlling and regulating electric circuits generally, for instance in
a system of electric distribution such as the three-wire system it is advantageous to
maintain the pressure on either side of the system the same, this can be effected by
winding the motor fields with wires in which flows a portion of the current flowing
in the positive and negative circuits to be controlled, so as to have a common field
for the two armatures which are preferably shunted on the field windings, one on
the positive and one on the negative side, and are so wound that when the pressure
on the two sides of the system is balanced so as to obtain the best results, they
revolve at the same speed but in opposite direct ons; the carrier of the centre
wheel of the differential gear, to which the armatures are geared in a similar
manner to that employed in the case of the are lamp, is adapted to operate switches,
resistances, valves or other controlling apparatus suitable to the source of power
from which the currents of electricity are obtained, any alteration in the balance
between the two sides of the system will cause the two armatures to run at
different speeds thereby moving the centre wheel carrier in such a direction as to
readjust the balance of the circuits by means of the before-mentioned switches,
valves, etc.
In another modification of my invention, I apply my improved regulator to
synchronizing motors, worked either by steam, electricity, fluid pressure, or other
motive power in this case I can either maintain the speed of the motor to be
controlled constant as compared with a machine or apparatus revolving at a
standard speed, or I can ensure a uniformn speed or a uniform difference in speed
between two motors. In the first case 1 cause the standard speed required to be
communicated to one of the two outer wheels of the differential gear, the other
wheel being driven by the motor to be governed, the carrier of the centre wheel is
caused to act, either directly or through the medium of an electric relay operating
a motor, on switches, resistances, valves or other controlling apparatus, suitable to
the special form of motor to be controlled. In the second case the two motors to
be synchronized are connected in any suitable manner to the two outside wheels of
the differential gear, the carrier of the centre wheel is then adapted to operate
either directly or through the medium of a suitable relay, the controlling apparatus
suitable to the special form of motors as before.
In the accompanying drawing I have shown a diagramatic view of my invention
adapted for controlling an electric are lamp. A and B are the two armatures,
A is wound with fine wire and is connected as a shunt on a portion S¹ of the fine
winding S, which is connected at X and Z as a shunt on the arc, B is wound with
thick wire and is connected at H and I as a shunt on the thick winding M which
is connected in series with the are. c+ and c are the positive and negative
carbons respectively. F.F. are the field inagnets, P. P. are the armature spindles,
T. T' are bevel wheels fixed thereon and adapted to engage with the bevel
wheels G. G the pinions of which are fixed in the cylindrical carrier W, the bevel

page_text: wheels T. T' together with the bevel wheels G. G¹ and the carrier W form the
differential gear above referred to.
a
The action of the apparatus is as follows, when the current is turned on to the
lamp and assuming that the carbons are apart the fine winding S of the field
magnets receives a certain amount of current, thereby magnetizing the field
magnets, at the same time the armature A also receives a small current, and
immediately begins to revolve, the armature B, however, in which no current is
flowing remains stationary, the result is that the centre wheels G. G₁ of the
differential gear run round on the stationary wheel T" carrying with them the
carrier W. causing it to turn in such a direction as to cause the carbons, through
the medium of the before-mentioned worm wheel and screwed rod to approach each
other, the moment the carbons touch the coils S. S. loose their strength and the
main current flows through the coils M. M. magnetizing the fields and sending
portion of the current through the armature B., which begins to revolve in an
opposite direction to the armature A, which is now stationary, the carbons therefore
become separated, and the arc is formed, the moment the arc is formed the
armature A begins once more to revolve and continues to increase in speed until the
arc is of the normal length, at the same time the armature B decreases in speed as
the current falls until the current flowing through the lamp and the potential on
the arc are normal, in which case both armatures revolve at the same speed but in
opposite directions, so that the cylindrical carrier W remains stationary, as the
carbons burn away and the arc in consequence become longer the pressure will rise
and the armature A will increase in speed over B which will also decrease, causing
the carrier W to revolve so as to feed the carbons together, should the arc become
too short the armature B will increase in speed as the current increases and the
carbons will be drawn apart to the proper extent.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
First. An improved rotary electrical differential controlling device, consisting of
an electric motor or motors having a common field, or fields of equal strength, and
two separate armatures, the said armatures being mechanically connected through
the medium of a differential gear, the current flowing in the said armatures being
derived from the circuits to be controlled, the winding of the two armatures being
so arranged and proportioned that when current flowing in the circuits to be
controlled is normal the armatures will revolve at equal speeds but in opposite
directions, the differences of speed of the armatures when the circuits to be
controlled vary from the normal is utilized through the medium of the differential
gear to operate devices by means of which the circuits to be controlled are brought
back to the normal, substantially as described.
Second. In an electric arc lamp the improved rotary electrical differential
controlling device substantially as shown and described and for the purpose set
forth.
Third. The improved rotary electrical differential controlling device substantially
as described and for the purposes set forth.
A. L. SHEPARD.