improvements in the Construction and Application of Induction Coils.
Year: 1884

page_text: This Specification was, upon the 21st day of August 1890, Amended under
Sections 18 to 21 of the Patents, Designs, and Trade Marks Act, 1883.
improvements in the Construction and Application of
Induction Coils.
We, JOHN HOPKINSON F.R.S. of 4 Westminster Chambers in the City of
Westminster and EDWARD HOPKINSON of 29 Princes's Street Manchester, Engineer
do hereby declare the nature of said Invention for "IMPROVEMENTS IN THE
CONSTRUCTION AND APPLICATION OF INDUCTION COILS" to be as follows:-
Our Invention relates to improvements in the construction and application of
induction coils. It has been demonstrated that it is practicable to work two or
more nlternate current dynamo-electric machines coupled parallel to each other
onto the same system of conductors also that an alternate current machine may be
used as a motor. These results depend upon the self induction of the machine and
in many machines this is too small to be efficient. In such cases we pass the
current from the machine through a self induction coil. We prefer to make this
Coil in such a manner that the core forms a complete magnetic circuit.
This inny
be best attained by making a ring of iron wire or of plates of sheet iron and
winding it with wire as a Gramme ring is wound but differently connected so that
the magnetic circuit inay be complete within the ring. The shape of this ring
may be varied provided its magnetic continuity be maintained. Such a ring
induction coil may be wound with two coils of wire and the current from the
machine be passed through one coil. The induced current in the other coil may
then be employed to produce a useful effect. We may regulate this induced
current in various ways. We may pass the current through a variable self
induction coil or we may vary the number of convolutions through which the
primary current passes. In either case it is advantageous to make the operation
automatic the necessary connections being made by means of clockwork or a train
of wheels controlled by an electro-inagnet more or less convolutions being used
according as the potential or current (as the case may be) varies. There are
advantages in adjusting the number of convolutions in the primary wire as by so
doing there is less disturbance of the current in the primary circuit than would
otherwise be the case. Or we may effect the automatic regulation by causing the
inovement of the core of the electro magnet either directly or by mechanism to alter
the level of mercury in a suitable vessel thereby making contacts and varying the
number of Coils in operation in the secondary or primary circuits. Our improved

page_text: induction coil possesses advantages over some others not only on account of its great
power for its small compass but also on account of the small electrostatic capacity
of the coils in relation to each other. The said induction coils may be used for
illuminating buoys the induction coil being placed in the buoy and the primary
current being brought thereto through an insulated cable whilst the secondary
current passes through an incandescent lamp on the top of the buoy, for this
purpose our improved apparatus possesses special advantages. The same principle
may be used in the construction of an inductorium the secondary coil being then
made of fine wire. An induction coil realizing the same fundamental idea is
obtained by using a straight iron core and completing the magnetic circuit by
means of iron wire outside the copper coils forming a cylinder the iron wires lying
parallel to the axis of the cylinder. Or the outer cylinder may be replaced by n
split iron tube. The regulation may then be effected by moving inwards or
outwards or backwards or forwards either the inner core or the outer cylinder.
Such induction coils can be used either alone or in combination with the ring form
previously described. When it is desired to run two alternate current machines
connected together parallel we sometimes enhance the control which exists between
a single core
them by passing their respective currents through two coils on
whereby the two currents not only have their self induction increased but also
have a direct inductive effect upon each other.
October 1984
J. HENRY JOHNSON,
47 Lincoln's Inn Fields, London, W.C.,
Agent for the said John Hopkinson
and Edward Hopkinson.

page_text: COMPLETE SPECIFICATION (AMENDED).
Improvements in the Construction and Application of
Induction Coils.
We, JOHN HOPKINSON, F.R.S. of 4 Westminster Chambers, Westminster in the
County of Middlesex and EDWARD HOPKINSON of 29 Princess Street, Manchester,
England, Engineer do hereby declare the nature of our invention for "IMPROVE-
AND APPLICATION OF INDUCTION COILS" and in
what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:—
MENTS IN THE CONSTRUCTION
Our Invention relates to improvements in the construction and application of
induction coils. It has been demonstrated that it is practicable to work two or
more alternate current dynamo electric machines coupled parallel to each other onto
the same system of conductors also that an alternate current machine may be used
as a motor. These results depend upon the self induction of the machine and in
many machines this is too small to be efficient. In such cases we pass the current
from the machine through a self induction coil. We prefer to make this coil in
such a manner that the core forms a complete magnetic circuit. This may be best
attained by making a ring of iron wire or of plates of sheet iron and winding it
with wire as a Gramme ring is wound but differently connected so that the
magnetic circuit may be complete within the ring. The shape of this ring may be
varied provided its magnetic continuity be maintained. Such a self induction coil
is described in Specification of a Patent granted to one of us N° 3362, 1881. But
such a ring induction coil may be wound with two coils of wire forming two
distinct circuits and the current from the machine be passed through one coil.
The induced current in the other coil may then be employed to produce a useful
effect. We may regulate this induced current in various ways. We may pass the
current through a variable self induction coil or we may vary the number of
In either case it is
convolutions through which the primary current passes.
advantageous to make the operation automatic the necessary connections being
made by means of clockwork or a train of wheels controlled by an electro magnet
more or less convolutions being used according as the potential or current (as the
case may be) varies. There are advantages in adjusting the number of convolutions
in the primary wire as by so doing there is less disturbance of the current in the
primary circuit than would otherwise be the case. Or we inny effect the automatic
regulation by causing the movement of the core of the electro magnet either directly
or by mechanism to alter the level of mercury in a suitable vessel thereby making
contacts and varying the number of coils in operation in the secondary or primary
circuits. Our improved induction coil possesses advantages over some others not
only on account of its great power for its small compass but also on account of the
small electrostatic capacity of the coils in relation to each other. The said induction
coils may be used for illuminating buoys the induction coil being placed in the buoy
and the primary current being brought thereto through an insulated cable whilst
the secondary current passes through an incandescent lamp on the top of the buoy,
for this purpose our improved apparatus possesses special advantages. The-same

page_text: principle--may-be--used-in-the-construction-of an induetorium-the--secondary-esit
being-then-made-of-fine-wire. An induction coil realizing the same fundamental
iden, is obtained by using a straight iron core and completing the magnet circuit by
means of iron wire outside the copper coils forming a cylinder the iron wires lying
parallel to the axis of the cylinder. Or the outer cylinder inay be replaced by a
split iron tube. The regulation may then be effected by moving inwards or out-
wards or backwards or forwards either the inner core or the outer cylinder. Such
induction coils can be used either alone or in combination with the ring form
previously described. When it is desired to run two alternate current machines
connected together parallel we sometimes enhance the contact control which exists
between them by passing their respective currents through two coils on a single core
whereby the two currents not only have their self induction increased but also have
a direct inductive effect upon each other.
And in order that our said Invention may be fully understood we shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the annexed sheet of drawings the same letters of reference
indicating corresponding parts in all the figures.
n
and
Figure 1 shews in side elevation and partial section a neutral mutual induction coil
or secondary generator constructed according to our Invention. a. is a core of hoop
iron or of iron wire magnetically continuous but having its sections separated froin
each other by insulating material to prevent waste of energy by currents circu-
lating in the iron. b is a framework of insulating material separating the 'several
coils of wire from each other and from the core. We prefer to make the frame of
noncombustible material such as slate (but this is not essential) as the mere
reversal of the magnetism of the iron heats it when the number of reversals per
second is considerable, it is also preferable to leave a space between the core
the frame b to admit of the circulation of air to cool the core. Upon the frame b
are wound a series of coils of insulated copper wire c to form the primary circuit
and alternately with these a series of similar coils are wound to form the
secondary circuit. The coils c may be coupled in any way but as a rule they will
be coupled in series. The coils & also may be coupled either parallel or in series or
otherwise according to the particular purpose they have to serve. We place the
secondary coils between the primary coils alternately in order to avoid the pro-
duction of consequent poles in the core but we consider it better not to place a
secondary conductor in close juxta position to each primary conductor, as is now
frequently done, as the electrostatic induction between the primary circuit and the
secondary circuit may cause a high difference of potential between the secondary
circuit and the earth. To regulate the potential or the current in the secondary
circuit various devices may he employed, for example from the fact that the current
in the secondary circuit depends not only on the resistance of that circuit but also
upon its self induction, we make use of this property by introducing into the
secondary circuit a self induction coil the coefficient of induction of which can be
varied. Another method is to vary the number of coils of the primary which are
operative, these being connected in series, the current is taken in at the first and is
returned to the primary circuit either at the junction of the first and second,
second and third or at the junction of any two successive coils at the pleasure of the
operator. In making use of this method it is necessary that those sections of the
primary circuit which are not used shall not be continuously short circuited.
is also desirable that the coils of the primary circuit successively connected to each
other in series should be as distant from each other as possible, thus if c' be the
first c³ should be the next in order, c³ may be the next and so on. This method
of adjustment may be made automatic by the action of an electro magnet, a
method of accomplishing this is shown diagrammatically in Figure 2, e is an
electro magnet, the coils of which may be either a shunt of the secondary circuit
if it is desired to control the potential of the secondary circuit or they may be in
series with the secondary circuit if it is desired to control the current therein,
This electro-magnet may operate in a variety of ways, one only of which we show.
It

page_text: direction to
is an armature carried on a lever g adjusted by a tightening spring h. c₁ c₂ and
so on represent the primary coils of the induction instrument are contact
blocks and a movable contact arm, the primary current enters at and after
traversing an adjustable number of coils of the primary circuit leaves by m,
the contact arm may be moved by a weight or spring in a
diminish the number of primary coils in use the pivot of the arm is in gear
through wheels n. o: with a spider wheel p the motion of which is stopped by a
detent on the lever g and is only released by the action of the magnet e
when the current or potential as the case may be is too great. As already stated it
is necessary to so arrange the mechanism that the contact arm k shall not con-
tinuously rest on any two blocks so as to short circuit any section of the primary
coil, this is effected as follows; a wheel r nakes one revolution or an aliquot part
of a revolution when the arm & passes from one block to the next-In the wheel r
are one or more notches & into which a projection on the lever g can drop, thus
the catch must remain disengaged unless the wheel r occupies such a position
that the projection is over a notch.
Figure 3 shows in elevation and part section another arrangement of our
secondary generator in which the iron coro instead of being continuous is only
approximately so. is a core comprised of a bundle of iron wires which can slide
to or fro in an insulating tube b, upon a frame on this tube are wound alternately
the primary coils c and the secondary coils d-The magnetic circuit is completed
by bundles of iron wires z laid parallel with the axis of the core and approxi-
mating to it at the ends-In this case the adjustinent of the current or potential
in the secondary circuit may be effected by drawing inwards or outwards the
core (L.
Having now particularly described and ascertained the nature of our said
Invention and in what manner the same is to be performed we declare that what
we claim is
1 Secondary generators having a closed or approximately closed magnetic
circuit of iron divided perpendicular parallel to the line of magnetic force substan-
tially as herein before described.
2 The--regulation--of--the--current--substantially--as-herein--described--from--a
secondary-generator-by-passing-the-secondary-enrrent-through--n-self-induction-evil
3--The-regulation--substantially--as--herein--described--of--the--current--from--&
secondary-generator-by-changing-the-number--of-convolutions-through-which--the
the-coefficient-of-induction-of-which-may-be-varied.
primary current-pusses:
4.-The-antomatic--electro-magnetic--regulation-of--the-number-of--primary-coils
in-a secondary-generator-substantially-as-and-for-the-purpose-herein-described.
Constructing secondary generators so that an approximate continuity of the
magnetic circuit is preserved substantially as hereinbefore described with reference
to Figure 3 of our drawing.

page_text: Induction Coils.
We, JOHN HOPKINSON F.R.S of 4 Westminster Chambers in the City of
Westminster and EDWARD HOPKINSON of 29 Princes's Street Manchester, Engineer
do hereby declare the nature of said Invention for "IMPROVEMENTS IN
CONSTRUCTION AND APPLICATION OF INDUCTION COILS" to be as follows:-
THE
Our Invention relates to improvements in the construction and application of
induction coils. It has been demonstrated that it is practicable to work two or
more alternate current dynamo-electric machines coupled parallel to each other
onto the same system of conductors also that an alternate current machine may be
used as a motor. These results depend upon the self induction of the machine and
in many machines this is too small to be efficient. In such cases we pass the
current from the machine through a self induction coil. We prefer to make this
Coil in such a manner that the core forms a complete magnetic circuit. This may
be best attained by making a ring of iron wire or of plates of sheet iron and
winding it with wire as a Gramme ring is wound but differently connected so that
the magnetic circuit may be complete within the ring. The shape of this ring
may be varied provided its magnetic continuity be maintained. Such a ring
induction coil may be wound with two coils of wire and the current from the
machine be passed through one cuil. The induced current in the other coil may
then be employed to produce a useful effect. We may regulate this induced
current in various ways. We may pass the current through a variable self
induction coil or we may vary the number of convolutions through which the
primary current passes. In either case it is advantageous to make the operation
automatic the necessary connections being made by means of clockwork or a train
of wheels controlled by an electro-magnet more or less convolutions being used
according as the potential or current (as the case may be) varies. There are
advantages in adjusting the number of convolutions in the primary wire as by so
doing there is less disturbance of the current in the primary circuit than would
otherwise be the case. Or we may effect the automatic regulation by causing the
movement of the core of the electro magnet either directly or by mechanism to alter
the level of mercury in a suitable vessel thereby making contacts and varying the
number of Coils in operation in the secondary or primary circuits. Our improved

page_text: induction coil possesses advantages over some others not only on account of its great
power for its small compass but also on account of the small electrostatic capacity
of the coils in relation to each other. The said induction coils may be used for
illuminating buoys the induction coil being placed in the buoy and the primary
current being brought thereto through an insulated cable whilst the secondary
current passes through an incandescent lamp on the top of the buoy, for this
purpose our improved apparatus possesses special advantages. The same principle
may be used in the construction of an inductorium the secondary coil being then
male of fine wire. An induction coil realizing the same fundamental idea is
obtained by using a straight iron core and completing the magnetic circuit by
means of iron wire outside the copper coils forming a cylinder the iron wires lying
parallel to the axis of the cylinder. Or the outer cylinder may be replaced by a.
split iron tube. The regulation may then be effected by moving inwards or
outwards or backwards or forwards either the inner core or the outer cylinder.
Such induction coils can be used either alone or in combination with the ring form
previously described. When it is desired to run two alternate current machines
connected together parallel we sometimes enhance the control which exists between
them by passing their respective currents through two coils on a single core
whereby the two currents not only have their self induction increased but also
have a direct inductive effect upon each other.
J. HENRY JOHNSON,
47, Lincoln's Inn Fields, London, W.C.,
Agent for the said John Hopkinson
and Edward Hopkinson.

page_text: Induction Coils.
We, JOHN HOPKINSON, F.R.S. of 4 Westminster Chambers, Westminster in the
County of Middlesex and EDWARD HOPKINSON of 29 Princess Street, Manchester,
England, Engineer do hereby declare the nature of our invention for "IMPROVE-
MENTS IN THE CONSTRUCTION AND APPLICATION OF INDUCTION COILS and in
"
what manner the same is to be performned, to be particularly described and
ascertained in and by the following statement :—
Our Invention relates to improvements in the construction and application of
induction coils. It has been demonstrated that it is practicable to work two or
more alternate current dynamo electric machines coupled parallel to each other onto
the same system of conductors also that an alternate current machine may be used
as a motor. These results depend upon the self induction of the machine and in
many machines this is too small to be efficient. In such cases we pass the current
from the machine through a self induction coil. We prefer to make this coil in
such a manner that the core forms a complete magnetic circuit. This may be best
attained by making a ring of iron wire or of plates of sheet iron and winding it
with wire as a Gramme ring is wound but differently connected so that the
magnetic circuit may be complete within the ring. The shape of this ring may be
varied provided its magnetic continuity be maintained Such a self induction coil
is described in Specification of a Patent granted to one of us N° 3362, 1881. But
such a ring induction coil may be wound with two coils of wire forming two
distinct circuits and the current from the machine be passed through one coil.
The induced current in the other coil may then be employed to produce a useful
effect. We may regulate this induced current in various ways. We may pass the
current through a variable self induction coil or we may vary the number of
convolutions through which the primary current passes. In either case it is
advantageous to make the operation automatic the necessary connections being
made by means of clockwork or a train of wheels controlled by an electro magnet
inore or less convolutions being used according as the potential or current (as the
case may be) varies. There are advantages in adjusting the number of convolutions
in the primary wire as by so doing there is less disturbance of the current in the
primary circuit than would otherwise be the case. Or we may effect the automatic
regulation by causing the movement of the core of the electro magnet either directly
or by mechanism to alter the level of mercury in a suitable vessel thereby making
contacts and varying the number of coils in operation in the secondary or primary
circuits. Our improved induction coil possesses advantages over some others not
only on account of its great power for its small compass but also on account of the
small electrostatic capacity of the coils in relation to each other. The said induction
coils may be used for illuminating buoys the induction coil being placed in the buoy
and the primary current being brought thereto through an insulated cable whilst
the secondary current passes through an incandescent lamp on the top of the buoy,
for this purpose our improved apparatus possesses special advantages The same

page_text: principle may be used in the construction of an inductorium the secondary coil
being then made of fine wire. An induction coil realizing the same fundamental
idea, is obtained by using a straight iron core and completing the magnet circuit by
means of iron wire outside the copper coils forming a cylinder the iron wires lying
parallel to the axis of the cylinder. Or the outer cylinder may be replaced by a
split iron tube. The regulation may then be effected by moving inwards or out-
wards or backwards or forwards either the inner core or the outer cylinder. Such
induction coils can be used either alone or in combination with the ring form
previously described. When it is desired to run two alternate current machines
connected together parallel we sometimes enhance the contact which exists between
them by passing their respective currents through two coils on a single_core
whereby the two currents not only have their self induction increased but also have
a direct inductive effect upon each other.
And in order that our said Invention may be fully understood we shall now
proceed more particularly to describe the same and for that purpose shall refer to
the several figures on the annexed sheet of drawings the same letters of reference
indicating corresponding parts in all the figures.
Figure 1 shews in side elevation and partial section a neutral induction coil or
secondary generator constructed according to our Invention a. is a core of hoop
iron or of iron wire magnetically continuous but having its sections separated from
each other by insulating material to prevent waste of energy by currents circu-
lating in the iron. b is a frame work of insulating material separating the several
coils of wire from each other and from the core. We prefer to make the frame of
noncombustible material such as slate (but this is not essential) as the mere
reversal of the magnetism of the iron heats it when the number of reversals per
second is considerable, it is also preferable to leave a space between the core a and
the frame b to admit of the circulation of air to cool the core. Upon the frame b
are wound a series of coils of insulated copper wire c to form the primary circuit
and alternately with these a series of similar coils d are wound to form the
secondary circuit. The coils c.inay be coupled in any way but as a rule they will
be coupled in series. The coils d also may be coupled either parallel or in series or
otherwise according to the particular purpose they have to serve. We place the
secondary coils between the primary coils alternately in order to avoid the pro-
duction of consequent poles in the core but we consider it better not to place &
secondary conductor in close juxta position to each primary conductor, as is now
frequently done, as the electrostatic induction between the primary circuit and the
secondary circuit may cause a high difference of potential between the secondary
circuit and the earth. To regulate the potential or the current in the secondary
circuit various devices may be employed, for example from the fact that the current
in the secondary circuit depends not only on the resistance of that circuit but also
upon its self induction, we make use of this property by introducing into the
secondary circuit a self induction coil the coefficient of induction of which can be
varied. Another method is to vary the number of coils of the primary which are
operative, these being connected in series, the current is taken in at the first and is
returned to the primary circuit either at the junction of the first and second,
second and third or at the junction of any two successive coils at the pleasure of the
operator. In making use of this method it is necessary that those sections of the
primary circuit which are not used shall not be continuously short circuited. It
is also desirable that the coils of the primary circuit successively connected to each
other in series should be as distant from each other as possible, thus if c¹ be the
first should be the next in order, c³ may be the next and so on. This method
of adjustment may be made automatic by the action of an electro magnet, a
method of accomplishing this is shown diagrammatically in Figure 2, e is an
electro magnet, the coils of which may be either a shunt of the secondary circuit
if it is desired to control the potential of the secondary circuit or they may be in
series with the secondary circuit if it is desired to control the current therein..
This electro-magnet may operate in a variety of ways, one only of which we show.

page_text: fis an armature carried on a lever g adjusted by a tightening spring h. o, c, and
so on represent the primary coils of the induction instrument, 7 are contact
blocks and a movable contact arm, the primary current enters at 7 and after
traversing an adjustable number of coils of the primary circuit leaves by m,
the contact arm k may be moved by a weight or spring in a direction to
diminish the number of primary coils in use the pivot of the arm k is in gear
through wheels n. o: with a spider wheel p the motion of which is stopped by a
detent 9 on the lever g and is only released by the action of the magnet e
when the current or potential as the case may be is too great, As already stated it
is necessary to so arrange the mechanism that the contact arm k shall not con-
tinuously rest on any two blocks so as to short circuit any section of the primary
coil, this is effected as follows; a wheel makes one revolution or an aliquot part
of a revolution when the arm k passes from one block to the next-In the wheel r
are one or more notches s into which a projection t on the lever g can drop, thus
the catch a must remain disengaged unless the wheel r occupies such a position
that the projection t is over a notch.
Figure 3 shows in elevation and part section another arrangement of our
secondary generator in which the iron core instead of being continuous is only
approximately so. a is a core comprised of a bundle of iron wires which can slide
to or fro in an insulating tube b, upon a frame on this tube are wound alternately
the primary coils c and the secondary coils d-The magnetic circuit is completed
by bundles of iron wires laid parallel with the axis of the core and approxi-
mating to it at the ends-In this case the adjustment of the current or potential
in the secondary circuit may be effected by drawing inwards or outwards the
core a
Having now particularly described and ascertained the nature of our said
Invention and in what manner the same is to be performed we declaro that what
we claim is
1st Secondary generators having a closed or approximately closed magnetic
circuit of iron divided perpendicular to the line of magnetic force substantially as
herein before described.
2nd The regulation of the current substantially as herein described from a
secondary generator by passing the secondary current through a self induction coil
the coefficient of induction of which may be varied.
3rd The regulation substantially as herein described of the current from a
secondary generator by changing the number of convolutions through which the
primary current passes.
4th The automatic electro magnetic regulation of the number of primary coils
in a secondary generator substantially as and for the purpose herein described.
5th Constructing secondary generators so that an approximate continuity of the
magnetic circuit is preserved substantially as hereinbefore described with roference
to Figure 3 of our drawing.