Year: 1888

page_text: Date of Application, 23rd Jan., 1888
Complete Specification Left, 8th Oct., 1888
Complete Specification Accepted, 15th Jan.,
1889
We, LAZARUS SIMON MAGNUS PYKE, Mechanical Engineer, and HARRY THEODORE
BARNETT, Electrician, both of Devonshire Place House, Regent's Park in the County
of Middlesex, do hereby declare the nature of our invention to be as follows:-
The greater part of this invention relates more especially to spark coils, but some
parts are applicable also to inductoria, or coils for other electrical purposes, and will
therefore be claimed broadly.
We construct the magnetic portion of our coils in such a manner, that it has the
form of a hollow cylinder of large diameter (that is to say one in which the ratio
between diameter and length is much larger than usual) open at both ends, the
magnetic poles being at the two ends.
By this arrangement of the magnetic material, the field is more concentrated and the
demagnetization more rapid than in any present method of construction.
The core should preferably be made of lengths of annealed iron wire placed
longitudinally.
We prefer to first construct the coil on a mandrel, then detach it and introduce the
magnetic material into the coil, to form a core of the shape previously described.
We effect the insulation in the following manner :
In winding the conductors, we place in the parts where high insulation is necessary,
a simple permeable material, such as paper, cardboard, porous earthenware &c., and
when the coil is wound, we impregnate the whole mass with a liquid insulator, for
instance hot paraffin wax.
To accomplish this impregnation, the coil is placed in a mould of a shape
corresponding to that of the finished article, and the whole is maintained at a
temperature sufficiently high to keep the insulating material at or above its melting
point, after which we allow it to flow slowly into the mould. As the material rises
in the mould, it will thoroughly permeate the coil and core, driving out the air
before it.
4
When the mould is sufficiently full, the source of heat is removed, and the whole
mass allowed to cool.

page_text: To obtain a very high insulation in our coils and condensers, we prefer to employ
the hard material known as ozokerit as the permeating insulator, because its tendency
to resist the disruptive effect of high tension currents and its specific inductive capacity
is much greater than that of paraffin wax, which has hitherto been usually employed
for this purpose.
To prevent unequal contraction of the insulating material on cooling, which we find
to be very detrimental (no matter how slowly the cooling proceeds), we arrange, that the
greater part of the mass is prevented from cooling rapidly, while another part
(preferably the base) is cooled as rapidly as may be convenient; the cooling thus
proceeds through the mass from this part, and the melted wax from above soaks down
to fill the space caused by the contraction of that which has cooled.
We also employ the above described wax and process of soaking and cooling for our
condensers.
We place the commutator or other accessories in the space surrounded by the core,
and operate them from the exterior by any suitable device.
FAIRFAX & WETTER,
433, Strand, London,
Agents for the Applicants.

page_text: Improvements in and Connected with Electric Coils.
We, LAZARUS SIMON MAGNUS PYKE, Mechanical Engineer, and HARRY THEODORE
BARNETT, Electrician, both of Devonshire Place House, Regent's Park, in the county
of Middlesex, do hereby declare the nature of our invention, and in what manner the
same may be performed, to be particularly described and ascertained in and by the
following statement :-
The greater part of this invention relates more especially to spark coils, but some
parts are applicable also to inductoria, or coils for other electrical purposes.
We construct the magnetic portion of our induction coils in such a manner, that it
has the shape of a hollow cylinder of large diameter, open at both ends; we make the
diameter of the cylinder preferably equal to one half or more of its length and confine
our claim to originality of invention within this limit. With this arrangement of the
magnetic material, the field is more concentrated and the demagnetization more rapid,
than in the present mode of construction of a similar size coil; also, a coil built on
this principle offers more surface for radiation and cooling by air currents—which
is of considerable importance in coils intended for continuous use. To further this
good effect, we may mount the coil in such a manner, as to allow free access for
air currents to the interior of the same. The core should preferably be made of
lengths of annealed iron wire placed longitudinally.
We prefer to first construct the coil on a mandrel, then detach it and introduce the
magnetic material into the coil to form a core of the shape above described, using a
central former between which and the coil the iron is packed.
The insulation is obtained in the following manner :
In winding the conductors, we place in the parts where high insulation is necessary,
a simple permeable material, such as paper, card-board, porous earthenware etc., for
instance, in the insulation of a single partition spark coil, one or more layers of paper
are wound between each layer of the secondary, the central partition being a card-
board ring extending in height about to the top of the secondary winding, and wound
over this, so as to overlap the secondary on each side, there may be several strips of
linen or similar substance, the thickness of card-board and linen winding being such
that the spark cannot pierce it. When the coil is wound and the core preferably in
place, we impregnate the whole mass with a liquid insulator, for instance, hot paraffin
wax. To accomplish this impregnation, the coil is placed in a mould of a shape
corresponding to that of the finished article, and the whole is maintained at a
temperature suffcient to heat the insulating material at or above its melting point,
after which we allow it to flow slowly into the mould. As the material rises in the
mould, it will thoroughly penetrate the coil and core, driving out the air before it.
We prefer to add the material of this impregnation by placing unmelted portions
successively in the interior of the former on which the core is built.
When the mould is sufficiently full, the source of heat is removed and the whole
mass allowed to cool. The insulation obtained by this process is very high. But as
the outer surface of the core cools before the interior, the contraction of the wax
causes cracking and probably partial vacua in the interior, thereby impairing the
insulation to a certain extent. The following process of cooling has been found to
obviate the aforesaid disadvantages.

page_text: While the bulk of the coil is covered to prevent cooling, the cooling is allowed to
proceed from one determined point, preferably the base, during which time the melted
wax from above soaks down to fill the space caused by the contraction of that which
has cooled. We effect this conveniently by leaving the coil on the plate on which it
was heated, removing the source of heat and covering the coil thoroughly with non-
conducting material. The plate, being in contact with the base of the coil mould, cools
first, and abstracts heat from the coil through its base. This method of insulating and
cooling is applicable also to resistance and other electric coils and to condensers, but,
the cooling of condensers proceeding from the side (as, of course, the wax could not
feed through the tin-foil), we employ weights before and during cooling, to render the
condensers more compact.
For obtaining the highest possible insulation, we employ preferably a hard mineral
wax known as ozokerit as the permeating insulator, on account of its tendency to
resist the disruptive effect of high tension currents, and because its specific inductive
capacity is much greater than that of paraffin wax which has been usually employed
for this purpose. Ozokerit, as purchased, is generally very impure and contains a
certain amount of moisture, both of which defects we eliminate by heating to about
212 Fahr., for some length of time, allowing the impurities to settle, and removing
the bottom wax which contains the same, while the pure top wax may be employed
as described.
We place the commutator or other accessories in the space surrounded by the core
and operate them from the exterior, by any suitable device.
In the accompanying drawing which represents a section of a spark coil, A is the
core, B the primary coil, C the secondary coil having a sheet of paper between
continuous layers of wire, D is the outer insulation covering, E is a partition or
insulating disc of cardboard, F, a wooden commutator spindle provided at the top with
a knob, G are contact pieces of brass, H, H, contact springs also of brass. To
facilitate cooling the cover plate may be perforated.
Having now particularly described the nature of our invention, and in what manner
the same is to be performed, we declare, that we claim :
1. In induction coils, a magnetic core having the shape of a hollow cylinder, the
length of which is less than twice its diameter and which has a pole at each end.
2. The method of insulating olectric coils, which consists in covering the metal, or
separating contiguous portions, by porous insulating material, and subsequently
impregnating the same with an insulating liquid, substantially as described.
3. The method of cooling electric coils and condensers which have been insulated
with a molten substance, which consists in protecting the bulk from loss of heat, and
then gradually cooling it from one extremity or other desired point, substantially as
described and for the purpose specified.
4. The use of ozokerit for insulating coils and condensers by impregnation, for the
purpose described.
5. A hollow inductorium having the commutator or other accessories placed in the
interior of the coil.
6. The combination, in a high tension inductorium, of two or more of the features
claimed by the preceding clauses.
T: 20th dow of Sontember 1888
Dated this 20th day of September 1888
L. S. M. PYKE.
H. T. BARNETT.
By Fairfax & Wetter,
433, Strand, London,
A vents.