Electrical Insulating Sheet.
Year: 1892

page_text: Date of Application, 2nd June, 1892
Complete Specification Left, 2nd Mar., 1893-Accepted, 15th Apr., 1893
PROVISIONAL SPECIFICATION.
Electrical Insulating Sheet.
I ARTHUR HENRY SALISBURY DYER, Electrician, residing at Schenectady,
in the County of Schenectady and State of New York, in the United States of
America, do hereby declare the nature of this invention to be as follows:-
The object of my invention is to provide for use in dynamos, motors and other
electric machinery and apparatus, an insulating plate of uniform thickness to be
placed between the bars of commutators and in other places where a homogeneous
insulating plate of uniform thickness is required. In carrying out my invention,
I take a sheet of iron and coat it with a varnish suitable for the purpose and place
upon said plate smaller, irregular pieces in such a relation to each other as to
cause the edges to overlap. Upon this layer of small and very thin pieces of
mica I place another layer with a coating of varnish intervening, and I proceed in
this manner until a plate of approximately the required thickness is formed.
I then heat the plate in an oven, or by means of steam, and while the solvent
of the varnish is being evaporated, I roll the plate so as to discharge the surplus
varnish, leaving only enough between the layers to cement them together. I then
subject the plate while it is still warm to very heavy pressure by means of a
hydraulic press, and afterward place it on a cold plate to chill and harden. It
is then sawed into the desired width and length and milled or planed to reduce
it to a uniform thickness. The last operation in the manufacture of the plate
of a little better finish is to apply to each side of the plate a scale of mica,
which is secured in place by means of varnish, when the plate is again steamed
and pressed. Mica in its natural state is hard and not of uniform thickness;
furthermore being porous between the laminæ, it is unfit for commutator insulation.
My improved built-up mica being free from these objections and having parallel
plane surfaces is perfectly adapted for use in commutators. It insures the uniform
spacing of the commutator bars, and secures an equal pressure between the bars
around the entire circumference of the commutator thus avoiding loose bars.
When desired, mica built in the manner described can be formed into curved
shapes by allowing it to become chilled while it is held by molds or clamps to
give it the desired form.
Dated this 10th dow of Mar 1800
AKTHUR 1. D. DI
F. W. Golby,
36. Chancery Lane, London, W.C., Patent Agent for the Applicant.
COMPLETE SPECIFICATION.
Electrical Insulating Sheet.
1 ARTHUR HENRY SALISBURY DYER of 293 Dock Street, in the City and
County of Schenectady, State of New York, United States of America,
Electrician, 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 means for insulating electrical conductors, commutator
segments, armature and field magnets, laminæ, and similar structures or parts
thereof.
My complete invention consists, briefly stated of a built up insulating plate
formed of a series of scales of non-comminuted mica of given various sizes and shapes

page_text: held together by a cement with their edges overlapping, a second, third and
fourth &c., layer as before superposed upon one another and cemented together and
finished by heating, rolling and pressing, and finally for certain cases equipped with
a layer of a larger scale applied one on both sides of the sheet and cemented
thereto, and if desired, heated, rolled and pressed as before.
More particularly described the product constituting my invention is of the
following nature. Natural mica, in the form of any of the ordinary minerals,
called technically, phlogopite, biotite, lepidomelane, muscovite, or lepidolite,
occurs in superposed layers, in an irregular manner, with air and moisture and
impurities, between the same, and with imperfect scales of mica occurring here and
there. These have been used in a limited number of devices for purposes of
insulation. In addition to the above defects, natural mica, in sufficiently large
pieces for most practical purposes, is very costly. My invention does away with
the above named defects and greatly cheapens the products, at the same time
accomplishing greater flexibility, strength, durability and superior insulating
qualities.
I take the elementary scales, obtained by splitting small or waste pieces of non-
comminuted mica sheets as thin as practicable. These scales, of course are,
necessarily, of various sizes and shapes; but it makes no difference how small they
are, as I am enabled to make use of all the qualities of waste mica in the market
without regard to size or shape. Each layer of the finished product, except the
outer, consists of these small mica scales cemented together into a sheet with their
edges overlapping. The cement consists, preferably, of copal varnish, but may be
shellac or similar insulating glue. Upon this layer is a like layer and the two are
held together by varnish or similar glue. Further, third, fourth &c. layers are upon
each other, each layer being substantially like the first.
Upon one or both sizes of the laminated plate so formed, are scales so large as to
cover numerous small scales, and the same are held together by an insulating
cement as before.
The first layer is formed and held temporarily, with varnish, upon a soap-stone
sheet-iron plate, and the built up mica sheet is heated, then rolled, pressed, chilled
and finally cut and sawed up into any desired shape and size as if it were so much
paper. By heating the sheet and clamping it rigidly in a curved shape before
cooling, and then chilling it rapidly it remains curved.
وو
By having the pieces irregular, the result obtained is correspondingly superior.
By "scales as used herein, I do not mean the small flakes known as comminuted
mica, obtained by grinding; but I mean the thinnest or elementary sheets obtainable
practically by cleavage, so that the sheets may be large enough to handle, one piece
at a time and build up the plate as described. The size used in practice varies from
one square inch to four square inches, according to the size of the natural waste
mica laminated sheets at hand. The pressure upon the plate while the varnish is
still wet and thin, squeezes the same into very thin films between the parallel layers
of elementary mica sheets.
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 :-
1. As a new article of manufacture, an electrical insulating sheet consisting of
the combination of laminæ, each formed of elementary mica scales of a given size
and of irregular shape, overlapping one another at their edges, electrically
insulating cement between the said laminæ, and between the scales at their over-
lapping edges, for the purpose, as set forth, of holding the same together and larger
scales covering and cemented to the said smaller scales.
2. As an article of manufacture, an electrical insulating sheet consisting of the
combination of scales of mica of a given size, a sheet of mica of larger size, and a
cement between the scales and the said sheets, for the purpose, as set forth, of
holding the same together into a compact, durable and efficient insulating sheet.

page_text: 3. As an article of manufacture, a built up insulating plate, consisting of the
combination of alternate layers of insulating cement and irregular arranged and
partially overlapped irregularly shaped elementary sheets of mica.
4. As an article of manufacture, a built up insulating sheet consisting of the
combination of alternate layers of mica scales with overlapping edges, and
insulating cement between the overlapping portions.
5. As an article of manufacture, a built up insulating sheet consisting of the
combination of alternate layers of mica scales with overlapping edges, and insulating
cement between the overlapping portions and an outer layer consisting of a series of
mica sheets of larger size than the said mica scales, applied and cemented to the
same.
6. As an article of manufacture, a built up insulating plate, consisting of layers
of elementary mica sheets all parallel to, and overlapping one another and parallel
insulating adhesive films between said layers.
7. A built up electrical insulating sheet, consisting of the combination of a layer
of non-comminuted mica sheets whose edges overlap one another, a film of insulating
cement, a second layer of non-comminuted mica sheets whose edges overlap one
another, a second film of insulating cement, a third layer of non-comminuted mica
sheets whose edges overlap one another, and so on to the desired thickness of
insulating sheet, all the layers and films being substantially parallel to one another,
and equal in length and width.
Dated this 2nd day of March 1002
ARTHUR HENRY SALISBURY DYER.
F. W. Golby,
36, Chancery Lane, London, W.C., Patent Agent for the Applicant.