Year: 1897

page_text: Date of Application, 9th Aug., 1897
I, WILLIAM THOMSON, BARON KELVIN OF LARGS, Professor of Natural Philosophy
in the University of Glasgow, North Britain, do hereby declare the nature of this
invention to be as follows:-
This invention relates to an improved coil for electric currents and is particu-
larly applicable for use for meters and ampere-guages. Among the objects of
my invention is to obtain a coil which will give, for very strong currents a more
uniform field than is attained by ordinary methods; and, generally, to minimise
the space unoccupied by the conducting material of the coil.
In carrying out my invention I take two copper tubes one smaller in diameter
than the other and I make one or more spiral cuts in each from near the top to
near the bottom. The spiral cuts in the two tubes are, right-handed in one,
and left-handed in the other. The smaller tube is placed inside the other with
the space between them occupied by air or solid insulating matter. The two
tubes are connected together at the top. The current goes up the copper spiral
of one tube and down the spiral of the other tube. I thus obtain a very uniform
field through almost the whole length of the cylindric space within the coil.
I may use four or more tubes cut spirally, and connected together as described
to form the coil. The several pairs may be connected either in series or in
parallel.
"
For currents of less than 50 or 100 amperes I build up the coil of pieces cut
out of sheet copper, each with a small hole in its centre, and a slot from this hole
to its outer edge. Each of these pieces is analogous to one of the
flat plates,
divided and bent," which I describe in my Specification No. 18035A of 1888.
The plan of connection, which I now describe, is a great improvement, especially
for the case in which the plates are much thinner than those used in my former
plan
In each plate the hole and the outer edge may be circular, but in general I
prefer to make the outer edge square, or oblong rectangular, so as to give more
surface for the emission of heat. One side of each piece is tinned for soldering,
the other is coated with very thin paper, mica, or other insulating material.
These pieces are placed together in pairs with the slots turned in opposite
directions; with two halves of the tinned sides in contact with one another, and
with the other halves of the tinned sides facing outwards. A large number of
equal and similar pairs of pieces, thus prepared, are placed similarly, one over
the other, on a metal rod through their centres, and are pressed firmly together
by means of screws and nuts at the ends of the rod, and suitable metal washers.
The whole structure is then heated to a sufficient temperature to melt the solder,
and after that is cooled. It is then removed from the rod used in the manu-
facture, and placed on a metal tube coated with insulating material, and it is
then ready for use.
A current between electrodes applied at its two ends passes

page_text: round this tube in a number of turns equal to the number of pairs of the com-
ponent discs.
Dated this 7th day of August 1897.
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Patent Agents.
Improveu o for Eectric Instruments.
I, WILLIAM THOMSON, BARON KELVIN OF LARGS, Professor of Natural Philosophy
in the University of Glasgow, North Britain, 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:-
-
This invention relates to an improved coil for electric currents and is particu-
larly applicable for use for meters and ampere-guages. Among the objects of
my invention is to obtain a coil which will give, for very strong currents a more
uniform field than is attained by ordinary methods; and generally, to minimise
the space unoccupied by the conducting material of the coil.
In carrying out my invention I take two copper tubes one smaller in diameter
than the other and I make one or more spiral cuts in each from near the top to
near the bottom. The spiral cuts in the two tubes are, right-handed in one,
and left-handed in the other. The smaller tube is placed inside the other with
the space between them occupied by air or solid insulating matter. The two
tubes are connected together at the top. The current goes up the copper spiral
of one tube and down the spiral of the other tube. I thus obtain a very uniform
field through almost the whole length of the cylindric space within the coil.
I may use four or more tubes cut spirally, and connected together as described
to form the coil. The several pairs may be connected either in series or in
parallel.
For currents of less than 50 or 100 amperes I build up the coil of pieces cut
out of sheet copper, each with a small hole in its centre, and a slot from this hole
to its outer edge. Each of these pieces is analogous to one of the "flat plates,
divided and bent," which I describe in my Specification No. 18035A of 1888.
The plan of connection which I now describe, is a great improvement, especially
for the case in which the plates are much thinner than those used in my former
plan.
In each plate the hole and the outer edge may be circular, but in general 1
prefer to make the outer edge square, or oblong rectangular, so as to give more
surface for the emission of heat. One side of each plate is tinned for soldering
the other is coated with very thin paper, mica, or other insulating material.
These pieces are placed together in pairs with the slots turned in opposite
directions; with two halves of the tinned sides in contact with one another, and
with the other halves of the tinned sides facing outwards. A large number of
equal and similar pairs of pieces, thus prepared are placed similarly, one over
the other, on a metal rod through their centres, and are pressed firmly together
by means of screws and nuts at the ends of the rod, and suitable metal washers.
The whole structure is then heated to a sufficient temperature to melt the solder,
and after that is cooled. It is then removed from the rod used in the manu-
facture, and placed on metal tube coated with insulating material, and it is
then ready for use. A current between electrodes applied at its two ends passes
round this tube in a number of turns equal to the number of pairs of the com-
ponent discs.
5

page_text: In order that my invention may be properly understood and readily carried
into effect I have hereunto appended one sheet of drawings, of which
Figure 1 is an elevation partly cut away and
Figure 2 is a vertical section of one form of coil.
Figure 3 is a plan and
Figure 4 an elevation of a portion of the second form of coil.
Figure 5 is a plan of one of the plates of which this coil is built up.
The coil shown in Figures 1 and 2 is built up of four tubes A, B, C, D, of differ-
ent sizes with air or other insulator between each. Each tube has one or more
spiral cuts from near the top to near the bottom. In tube A the spiral cut is
right-handed, in B the cut is left-handed, in C the cut is right-handed, and in D
the cut is left-handed. The tubes A and B are connected at the bottom, B and C
at the top, and C and D at the bottom as shown in Figure 2. The current goes
down the spirals in one tube, up the spirals in the second, down the spirals in the
third, and up the spirals in the fourth. I thus obtain a very uniform field
through almost the whole length of the cylindric space within the coil.
For currents of less than 50 or 100 amperes the coil is built up of pieces cut
out of sheet copper, one of these pieces is shown in plan at Figure 5. Each piece
has a small hole in the centre and a slot from this hole to the outer edge as shown.
One side of each plate is tinned for soldering the other side is coated with very
thin paper, mica or other insulating material. These pieces are placed together
in pairs with the slots turned in opposite directions and slipped into one another
so that two halves of the tinned sides may be in contact with one another and the
other sides of the tinned sides facing outwards. In Figure 3 if a¹ is the insulated
half of one disc a will be the tinned side of another, the other half of a being
underneath a¹ and in contact with, the tinned side of a¹ as shown in Figure 3,
which represents two of such pairs. A large number of equal and similar pairs
of pieces, thus prepared are placed similarly, one over the other, on a metal rod
through their centres, and are pressed firmly together by means of screws and
nuts at the ends of the rods, and suitable metal washers. The whole structure
is then heated to a sufficient temperature to melt the solder, and after that is
cooled. It is then removed from the rod used in the manufacture, and placed on
a metal tube coated with insulating material, and it is then ready for use.
current between electrodes applied at its two ends passes round this tube in a
number of turns equal to the number of pairs of the component discs.
A
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
The improved coils for use in electric instruments constructed substantially as
described.
BOTTOMLEY & LIDDLE,
154, St. Vincent Street, Glasgow, Applicant's Patent Agents.