Improvements in or connected with Electric Induction Coils and Transformers.
Year: 1896

page_text: PROVISIONAL SPECIFICATION.
Improvements in or connected with Electric Induction Coils and
Transformers.
I, ALFRED APPS, Scientific Instrument Maker, of 433, Strand, in the County of
London, do hereby declare the nature of this invention to be as follows:-
This invention relates more especially to the insulation between the primary and
secondary coils or between different sections of transformers, and has for its principal
object to avoid any unnecessary mechanical strains in the principal insulating tube
or insulating layer. I have found that, when an insulating material, such as glass,
ebonite, or shellac, is subject to mechanical strain and there is added an electrical
strain, the resistance to rupture is much decreased, and that such a combination may
easily occur in insulating tubes applied in the ordinary way, that is to say without
any provision being made for the free expansion and contraction of the insulating tube
in accordance with change of temperature.
I therefore employ in addition to the insulating tube an auxiliary tube or frame,
which supports the outer coil or coils and is sufficiently rigid to relieve the principal
insulating tube of any initial strains produced by the process of winding, or final adjust-
ment of parts, and which also leaves sufficient clearance to allow the free expansion and
contraction of the principal insulating tube. Instead of one auxiliary insulating and
supporting tube or frame, two or more may be used, so as to protect the insulating
tube both inside and outside, and to allow sufficient clearance for its expansion and
contraction both radially and axially. The principal insulating tube is preferably
fixed at one end by inserting it into a socket formed in an endplate, but it need not
be fixed at all, being simply inserted between two supporting tubes or contained in an
outer tube or tubes.
An insulating simple or compound tube arranged as described offers also the great
advantage, that it can be easily withdrawn endways, and a new tube inserted in its
place, without disturbing the primary or secondary winding.
The insulating tube may be composed of two or more concentric tubes, which may
or may not have longitudinal slits for easier expansion, or it may be composed of
several segments or circumferential plates, which are held in position by auxiliary
supporting tubes, plates, flanges or ledges.
In some forms of induction coils and transformers the primary may be separated
from the secondary winding by a set of insulating discs or rings, and the principal:
insulating disc allowed to. expand and contract in the same manner as the insulating
tube described above.
For keeping the insulating tube in position, a light spring may be placed between
the end of the tube and the base plate or cover plate, or the said plate or the tube
itself may be armed with spring clips.
Insulating tubes or discs or plates arranged as described, may be inserted and be
easily removed, not only between the primary and the secondary winding of an
induction coil or transformer, and between a coil and a magnet or iron core, but also
between different sections of the same coil or winding, the said insulating plates
being semicircular or overlapping so as to be removed radially in case the winding
has a great length and is arranged in two or more sections.
The principal insulating tube or plate or frame may be made of glass, ebonite.

page_text: shellac, or other solid insulating material, and the supporting tube or tubes or its
equivalent may be made of the same or of a different material."
Dated this 4th day of July, 1896.
COMPLETE SPECIFICATION.
Improvements in or connected with Electric Induction Coils and
Transformers.
I, ALFRED APPS, Scientific Instrument Maker, of 433, Strand, in the County of
London, 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 more especially to the insulation between the primary and
secondary coil or between different sections of transformers, and has for its
principal object, to avoid any unnecessary mechanical strains in the principal
insulating tube or insulating layer. I have found, that, when an insulating.
material, such as glass, ebonite, or shellac, is subject to mechanical strain and.
there is added an electrical strain, the resistance to rupture is much decreased.
Such a combination may easily occur in insulating tubes applied in the ordinary
way, that is to say, without any provision being made for the free expansion and.
contraction of the insulating tube in accordance with changes of temperature.
I therefore employ in addition to the insulating tube an auxiliary tube or
frame, which supports the outer coil or coils and is sufficiently rigid to relieve
the principal insulating tube of any initial strains produced by the process of
winding or final adjustment of parts, and which also leaves sufficient clearance to
allow the free expansion and contraction of the principal insulating tube. Instead
of one auxiliary insulating and supporting tube or frame, two or more may be
used, so as to protect the ordinary insulating tube both inside and outside and
to allow sufficient clearance for its expansion and contraction both radially and
axially. The ordinary or principal insulating tube may be fixed at one end by
inserting it into a socket formed in an endplate, but it need not be fixed at all,
being simply inserted between two supporting tubes or contained in an outer
tube or tubes.
An insulating tube, protected by a supporting tube or tubes as described; offers
also the great advantage, that it can be easily withdrawn endways, and a new
tube inserted in its place, without disturbing the primary or secondary winding.
The insulating tube may be composed of two or more concentric tubes, which
are held in position by auxiliary supporting tubes, plates, flanges, or ledges.
In some forms of induction coils and transformers the primary may be separated
from the secondary winding by a set of insulating. discs or rings, the principal
insulating disc being protected by one or two supporting discs or rings, so that it
may expand and contract in the same manner as the insulating tube described
above.
"For keeping the insulating tube in position, a light spring may be placed between
the end of the tube and the base plate or cover plate, or the said plate or the tube
itself may be armed with spring clips.
Removable insulating tubes, rings or plates arranged as described may be
inserted not only between the primary and the secondary winding of an induction
coil or transformer, or between a coil and a magnet or iron core, but also between

page_text: different sections of the same coil or winding. Such insulating plates or rings.
are preferably semi-circular or provided with a radial slot, so that they can.be
removed radially and replaced or substituted for an entire disc first employed,
which arrangement saves much trouble in case the winding has a great length
and is composed of two or more sections.
The principal insulating tube, plate, or ring may be made of glass, ebonite,
shellac, or other solid insulating material, and the supporting tube or its
equivalent may be made of the same or of different material.
Instead of a solid supporting tube or disc, a perforated tube or open frame
may be used in conjunction with a solid insulating tube or layer. .:
1
In the accompanying drawing, Fig. 1 is an axial section of an induction coil
embodying an example of my invention.
Figs. 2 and 3 represent insulating half-discs between two sections of the
secondary coil.
A is the primary coil provided with a core C of iron wires; B the secondary
coil divided into parallel sections by means of insulating rings or discs D, D',
shown in detail by Figs. 2 and 3. These rings are provided with radial openings
d, d, which have the width of their inner diameter and are alternately turned
in opposite directions, so that two rings form a complete insulation and each can
be replaced by another, without uncoiling the secondary winding.
E is the principal insulating tube, made of one piece, and F the supporting
tube, which surrounds the tube E and carries the weight of the secondary
winding B.
These tubes are held in place at each end by a screwed upright or stand G
and a screw cap H. The said stand abuts against a short tube I resting on the
end plate or cover K of the secondary coil.
If one of the caps H and the corresponding upright G are unscrewed, after the
wire ends passing through the said upright have been drawn out of the same,
the principal insulating tube E, together with the parts enclosed by the same, may
be caused to slide out.by holding the apparatus in an upright or slanting position,
and the insulating tube can then be replaced, or the primary coil examined or
repaired, without disturbing the secondary winding.
M are sleeves, or tubular stays, inserted between the end plates or covers of the
primary coil A and the screw caps H, to keep the primary coil in the middle of the
tube E.
The primary coil A is preferably also arranged in parallel sections, so that it
can be easily detached.
In the case of closed circuit transformers, the iron core projects beyond the
ends of the principal insulating tube E, in order to form a magnetic connection
with the next core.
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:
1. In an electric induction coil or transformer, the combination of a simple or
compound insulating tube or layer of insulating material, with a supporting tube
or frame adapted to hold conductor windings and to relieve the insulating tube
or layer of mechanical strains, substantially as described and for the purpose
specified.
2. In an electric induction coil or transformer, the combination of two or more
removable insulating layers, inserted between the primary and secondary windings
or between different sections of the same winding, each layer being adapted for
removal without disturbing the conductor windings and forming with the other
layer or layers a complete insulation, substantially as described.
3. An electric induction coil or transformer having between the primary and
the secondary coil an insulating and a supporting tube, and between adjoining

page_text: sections of the secondary coil a pair of radially removable discs or rings, substantially
as described and shown by the drawings.