Improvements in Materials, and Methods of Preparing the same, for Bases of Electrical Instruments and for other Electrical Insulating Purposes.
Year: 1889

page_text: Date of Application, 7th Feb., 1889
Complete Specification Left, 17th Oct., 1889-Accepted, 11th Jan., 1890
PROVISIONAL SPECIFICATION.
Improvements in Materials, and Methods of Preparing the same,
for Bases of Electrical Instruments and for other Electrical
Insulating Purposes.
I FREDERICK LAWRENCE RAWSON of No. 11 Queen Victoria Street in the City
of London Electrical Engineer of the Woodhouse & Rawson Electric Manu-
facturing Company Limited of the same address, do hereby declare the nature of
this invention to be as follows :-
My invention relates to improvements in the materials used for the bases of
electrical switches and similar instruments and is applicable to other electrical
purposes such as easing for wires, conduits for cables, and generally for bases of
inachines and instruments where insulation is required.
I take for the body of our material a non-inflammable substance such as Portland
cement or other material which is capable of being mixed with suitable liquid or
liquids into a plastic mass and moulded into suitable forms and which will gradually
harden to such an extent as is found advisable.
I may use in conjunction with such cement a suitable proportion of plaster of
Paris or similar close grained powder which may have the effect of producing a
suitable closeness of grain and may counteract the tendency to shrink which generally
occurs with most cements.
Or I may use in conjunction with such cement a siliceous powder such as sand in
order to produce a suitable degree of hardness.
I select such cements and liquids as shall produce a material which shall not
harden too rapidly and which when dry shall possess a suitable degree of
porosity.
The bases or other forms may be removed from the moulds as soon as they are
hard enough to prevent alteration of form and may then be dried at such temperatures
and for such time as to produce the requisite degree of hardness, & remove the
greater part of the uncombined liquid or liquids.
Or they may be further chemically treated in such a way as to produce further
concentration of structure to a suitable degree without considerable alteration of form
or dimensions. For instance the cement and plaster articles may be dipped in silicate
of soda for a suitable time. They may then be dried at suitable temperatures and
for suitable lengths of time.
The article may then be immersed in a bath of ozokerit or nigrite or similar
paraffin of high melting point at a suitable temperature and for a suitable time to
secure such saturation as is advisable. The bath may then be allowed to cool and the
articles withdrawn at such a temperature as shall have allowed the requisite degree
of saturation to take place.
(In place of using the above mentioned material or materials I may employ
porcelain of a porous nature which has been baked at a comparatively low temperature.
This substance may be moulded previous to baking into any requisite form and after
baking it may be dried and treated at suitable temperatures in a similar way to that
mentioned above.)
I may apply one or other of the above materials to the production of a large
variety of articles where the properties of the resulting substance make it particularly
applicable. Amongst these I may enumerate the bases of electrical instruments
generally, casing for carrying electric wires, conduits for electric cables, tubes for
carrying electric wires through floors or elsewhere, dynamo and transformer bases,
and many other such articles.

page_text: The materials may be moulded into almost any variety of form. The strength
may be made very great by suitable treatment and the insulation may be raised to a
very high point by a suitable saturation with the paraffin. The suturation may be
either effected by dipping as above mentioned or by forcing the paraffin material
into the pores under pressure from a force pamp or the use of a vacuum
chamber.
I sometimes prefer to make this insulating material as hereafter described. An
intimate mixture of three parts by measure of Portland coment and one part of plastor
of Paris to be mixed with a minimum quantity of water to form a thick paste, then
introduced into the mould and allowed to set, and upon removal exposed to the
air to dry for from say five to ten days until the requisite hardness is obtained. I
then dry this at a temperature of from 220 to 230° Falt. and place this mixture in
a bath of paraffin of high melting point at about the same temperature until
Katurated.
Dated this with day of February 1009.
COMPLETE SPECIFICATION.
Improvements in Materials, and Methods of Preparing the same,
for Bases of Electrical Instruments and for other Electrical
Insulating Purposes.
I, FREDERICK LAWRENCE RAWSON of No. 11 Queen Victoria Street in the City of
London Electrical Engineer, of the Woodhouse and Rawson Electric Manufacturing
Company Limite of the same address, 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 the manufacture of bases for electrical switches or instru-
ments, casings or conduits for conductors, and generally for those parts of electrical
apparatus where insulation is required, the object which I have in view being to
adapt for these purposos inexpensive and incombustible materials which can be
readily moulded into the shapes required.
For this purpose 1 intimately mix about six parts by measure of Portland cement
with about one part of plaster of Paris, and with sufficient water to convert the
mixture into a paste suitable for moulding. In some cases I mix with the above
proportions of cement and plaster of Paris a small proportion not exceeding two
parts of clean sand. I mould this paste to the form desired, coring in it such holes
as may be necessary for bolts or other attachments, and moulding in it such metal
parts as may have to be permanently attached to it. After the material luas set in
the mould, I remove it and axpose it to be dried slowly at a moderate temperature
during ten days or more, the time depending on the mass that has to be dried and
the degree of hardness required. The moulded article may be farther hardened by
immersing it for a day or more in a solution consisting of equal parts of silicate of
soda and water. When the moulded article is sufficiently dry and hard I heat it to
about 220° or 230° F. and then plunge it in a bath of molten ozokerit or parallin
wax or material which is the heavy oil or residue of distillation of parathin, petroleum
or analogous substances having a high melting point. In many cases the moulded
article may be placed in the molten material without preliminary heating. When
the molten material has cooled down to about 200° F. I remove the moulded article
from the bath and clear it of the superfluous matter adhering to it.
In making boxes or tanks which cannot be conveniently immersed in a bath of
the molten material, I adopt the following method of proceeding. I provido a closed
metal vessel that can be put inside tho moulded article leaving a space all round
it to receive the imprognating substance. I charge this vessel with steam at a
temperature of 220° to 230° whereby the impregnating material is melted and
kept in a melted condition as it soaks through the thickness of the box or tank.

page_text: The article thus impregnated with the oily matter is hard, strong and incom-
bustible, and has high electrical resistance so that it forms a good insulator and,
being protected against access of moisture, it permanently retains its insulating and
other properties.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed I declare that what
I claim is
1. The method of preparing bases and other insulating parts of electrical apparatus,
by moulding them of a mixture of Portland cement and plaster of Paris, drying the
moulded articles, heating them and impregnating them with heavy oil, substantially
as described.
2. Bases and other insulating parts of electrical apparatus consisting mostly of
Portland cement and plaster of Paris moulded to shape and impregnated with heavy
oil or analogous material, substantially as described.
Dated this 17th day of October 1889.
ABEL & IMRAY,
Agents for the Applicant.