Improvements in Electrical Resistances.
Year: 1897

page_text: Date of Application, 2nd Nov., 1897
Complete Specification Left, 30th July, 1898-Accepted, 8th Oct., 1898
Improvements in Electrical Resistances.
WE, THOMAS EDWARD GAMBRELL, of Grasmere, Allfarthing Lane, Wandsworth,
and ARTHUR FREDERICK HARRIS, of Roslin, 57, Acre Lane, Brixton, Electricians, in
the County of London, do hereby declare the nature of this invention to be as
follows:-
Our invention applies to the construction of carbon resistances and consists in
the mixing of finely divided carbon in the form of lamp-black, gas-black, ivory-black,
vegetable-black, or the like with a suitable liquid medium to enable it to be applied
to a solid insulating substance such as baked wood, ground glass, ebonite, celluloid,
fibre, or other suitable insulating material for the construction of electrical resistances
capable of more exact adjustment and greater constancy than has hitherto been
obtained with carbon resistances.
Very good results may be obtained by mixing carbon in any of its different forms
with methylated spirits, alcohol, acetone, or other liquid which readily volatilizes and
a sufficient quantity of shellac, size, or other binding material for the purpose of
constituting a cement which when the volatile constituent has evaporated will hold
the carbon molecules together and to the wood or other base used-the proportions
used will depend on the resistance required for any given area.
The wood or other insulating material can be made of any convenient shape or
form and mounted in a protective case or covering and fitted with suitable terminals
binding screws, or the like for making connections.
The following is a convenient method of adjustment :-
==
To get an exact value.--If the resistance is too high apply more of the mixture.
If too low reduce by scraping or any other equally convenient method the surface of
the above after it has been allowed to set.
1-
1000
TOM. E. GAMBRELL,
A. FREDK. HARRIS.
Improvements in Electrical Resistances.
THOMAS EDWARD GAMBRELL, "Grasmere," 61, Allfarthing Lane, Wandsworth, S.W.,
Electrician, and ARTHUR FREDERICK HARRIS, 57, Acre Lane, Brixton, S.W.,
Electrician, both of 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 :-
Our invention applies to the construction of carbon resistances, and consists in the

page_text: use of finely divided carbon in any of its various forms, mixed with any suitable
liquid medium or mediums to enable it to be applied to a solid insulating substance
as ground glass, celluloid, ebonite, übré, or the like for the construction of electrical
resistances.
The general method of applying the patent is the following
--
Carbon is taken in any of the forms above referred to and mixed with methylated
spirit, alcohol, acetone or other volatile solvent; a certain amount of shellac size or
other binding material is then added (which may have been previously dissolved in
a suitable medium such as methylated spirits, naptha or the like) the whole forming
a thin paste which may easily be applied to the desired insulating base by means of a
brush or other suitable means. The volatile constituent then evaporates leaving
the carbon uniformly deposited and securely fixed to the insulating base to which
the mixture has been applied.
as ground glass, celluloid, ebonite, übré, or the like for the construction of electrical
resistances.
The general method of applying the patent is the following
Carbon is taken in any of the forms above referred to and mixed with methylated
spirit, alcohol, acetone or other volatile solvent; a certain amount of shellac size or
other binding material is then added (which may have been previously dissolved in
a suitable medium such as methylated spirits, naptha or the like) the whole forming
a thin paste which may easily be applied to the desired insulating base by means of a
brush or other suitable means. The volatile constituent then evaporates leaving
the carbon uniformly deposited and securely fixed to the insulating base to which
the mixture has been applied.
The following proportions have been found to give satisfactory results.
Take 4 parts by volume of methylated spirits.
2 parts by volume of gas-black.
1 part of a 10% (ten per cent.) solution of shellac in rectified naptha and
mix the constituents well together and apply as described above.
These proportions may be slightly altered to suit the resistance required, also the
application of more or less of the mixture produces a different value in the resistance.
The insulating material carrying the deposited carbon, being mounted in a
suitable box or case with terminals, so as to enable connection to be made for using
the resistance.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
The mixture of finely divided carbon in any of its forms as detailed above, with a
mixture of a volatile solvent and a binding cement, which enables it to be applied to a
convenient insulating material, and is such, that the volatile constituent having
evaporated, the carbon will remain securely deposited, and uniformly fixed to the
insulating substance for use as an electrical resistance.
Dated his ooth
Γ
T
1000