IMPROVEMENTS IN THE PREPARATION OF MATERIALS TO BE EMPLOYED for the PurPOSES OF ELECTRIC INSULATION
Year: 1881

page_text: LETTERS PATENT to John Ambrose Fleming, of University College,
Nottingham, Doctor of Science and Professor of Physics, for an Invention
of "IMPROVEMENTS IN THE PREPARATION OF MATERIALS TO BE EMPLOYED
for the PurPOSES OF ELECTRIC INSULATION.”
PROVISIONAL SPECIFICATION left by tho said John Ambrose Fleming at
the Office of the Commissioners of Patents on the 5th December 1881.
JOHN AMBROSE FLEMING, of University College, Nottingham, Doctor of Science
and Professor of Physics. "IMPROVEMENTS IN THE PREPARATION OF MATERIALS
TO BE EMPLOYED FOR THE PURPOSES OF ELECTRIC INSULATION."
My Invention relates to further improvements in the preparation of materials to
be employed for the purposes of electric insulation, and has reference to a former
Invention, in respect of which I obtained Letters Patent, dated the 23rd April 1881,
No. 1762.
According to my present Invention I take wood or bran or other fibrous
material in a finely divided condition, and having thoroughly desiccated the saine
saturate or impregnate it with melted paraffin or mineral wax, or mixtures of
paraffin or mineral wax and rosin, or with other allied substance, either under
pressure or not. I then mould under pressure the material thus treated, so as to
produce articles of a shape adapted to the purposes for which they are to be
applied.
In order to obtain a better imitation of ebonite I may add to the material in the
course of preparation lamp black, vegetable black, or other black coloring matter
of such a nature and in such proportions as not to interfere with the insulating
quality of the finished product. 1 may also impart additional hardness by the
employment of sulphur or other substance capable of producing the saine result.
For certain applications I substitute papier maché for finely divided wood, bran, or
other fibrous material, the papier maché being dried and disintegrated, and the
finely divided product saturated or impregnated with melted paraffin or mineral
wax, or a mixture of parattin or mineral wax and rosin, or with other allied
substance, and moulded as hereinbefore described.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Ambrose Fleming in the Great Seal Patent Office on the
22nd February 1882.
JOHN AMBROSE FLEMING, of University College, Nottingham, Doctor of Science
& Professor of Physics. " IMPROVEMENTS IN THE PREPARATION OF MATERIALS
TO BE EMPLOYED FOR THE PURPOSES OF ELECTRIC INSULATION."
My Invention relates to further improvements in the preparation of materials to
be employed for the purposes of electric insulation, and has reference to a former
Invention, in respect of which I obtained Letters Patent, dated the 23rd April 1881,
No. 1762.
According to my present Invention I take wood in a finely divided condition, or
other vegetable fibrous material, such for example as wood flour, bran, straw,
cotton, jute, hemp, papier maché, in a finely divided condition, and having
thoroughly desiccated the same by drying it in an oven, or in a current of hot air,
or in the manner described in the Specification to my said former Letters Patent, or
by any other equivalent method, I saturate or impregnate it with melted paraffin
wax, or mixtures of paraffin wax and resin.
To accomplish this the material, which may be fine sifted saw-dust or ordinary
saw-dust reduced to a state of finer division, or any of the other materials above
mentioned in a finely divided stato, is heated to a temperature somewhat above
that of the liquefying point of the paraffin wax or mixture used, and maintained
at such temperature, while the paraffin wax or mixture, which must also be at such
a temperature as to be thoroughly liquid, is poured upon it. The whole is then
maintained at such a temperature that the paraffin wax or mixture remains
perfectly liquid until the dry saw-dust or other material has absorbed as much of
it as it is capable of doing. No more of the paraffin wax or mixture should be used
than can be so absorbed, as an excess would ronder the resulting material softer
and less suitable for the purposes for which it is intended to be used.
The whole is stirred during the process of saturation, and becomes a thick pasty
mass, which is then placed in moulds of the required shape, and subjected to
pressure by a screw or hydraulic press, or by some other equivalent method.
The mould should be warmed previously to the mixture being put into it, and
uuintained at such temperature until the pressure has been applied so as to prevent
the parallin wax or mixture being solidified before the pressure is applied. The
greater the pressure and the longer the time it is maintained, the harder and
stronger the resulting matorial will bo, but there is no necessity to maintain the
pressure for more than a few ininutes.
For the purpose of obtaining a material of great homogeneity and strength, I
take the tinest wood flour, and having desiccated the same thoroughly in a current
of hot air, or in an oven, or by any other convenient process, I impregnate it with
the parallin wax or mixture used under pressure, in a manner substantially similar
to that described in my said former Specification as applied to the treatment of
wood in bulk or in mass.
The wood flour thus treated is subjected to slight pressure in order to eliminate
all superfluous or adherent impregnating material, and is, then moulded under
pressure into any form adapted to the purposes for which it is to be applied; or I
may introduce the saturated material into a perforated mould, and express. the
superfluous impregnating matorial through the intertices of the mould by the act
of applying pressure in order to mould the material into shape.
A iuaterial is thus obtained formed by the cohesion of small particles of wood
each of which has been separately impregnated and rendered insulating by the
process described in my said former Specification.

page_text: I have found in practice that a mixture of, say, about 3 parts by weight of
paraffin wax and 1 part by weight of resin gives good results, but other propor-
tions may be employed. I have found however that in all cases it is desirablo to
have the paraffin wax largely in excess of the resin, the object of the resin being
chiefly to raise the melting point of the impregnating material and reduce the
brittleness of the same.
In order to obtain a better imitation of ebonite, or to impart to the material any
requisite shade of color, I may add to the material in the course of preparation
a small quantity of lamp black, vegetable black, or other vegetable coloring matter
of such a nature and in such proportions as to give the required shade.
The amount of such coloring matter must be small, compared with the mass to
which it is added, that it may not interfere with the insulating qualities of the
finished product.
There is however little danger of this, as a very small amount of such coloring
matter will give a sufficiently deep shade. It is most conveniently added to the
saw dust or other material used when it has undergone desiccation, and before the
paraffin wax or mixture is poured upon it, and the coloring matter should be
thoroughly stirred up with the dry material, so as to disseminate it equally
throughout the mass.
14
By the term "paraffin wax," as used in this my Specification, I mean any of the
substances known by the ordinary names of ozokerite or solidified petroleum or
mineral wax, or more strictly a substance whose main constituents are hydro-
carbons, the composition of which is denoted by the formula C. H+; and by the
term "resin," as used in this ny Specification, I mean any of the substances
known as "resin " or " rosin," which are the exhudation of various species of pines
and firs.
The materials prepared according to my Invention I propose to designate
" insulite."
Having now described and particularly ascertained the nature of my said
Invention, and the manner in which the saine is or may be used or carried into
effect, I would observe in conclusion that what I consider to be novel and original,
and therefore claim as the Invention secured to me by the herein before in part
recited Letters Patent is,-
The preparation of materials to be used for the purposes of electric insulation by
the employment of wood or other vegetable fibrous material, as herein set forth, in
a finely divided condition, desiccated and saturated or impregnated with paraffin
wax, or with a mixture of paraffin wax and resin, in conjunction or not with other
substances, the whole being moulded under pressure, all substantially as hercin-
before described.
In witness whereof, I, the said John Ambrose Fleming, have hereunto set
my hand and seal, this Twenty second day of February, in the year of our
Lord One thousand eight hundred and eighty two.
JOHN AMBROSE FLEMING. (L.S.)