Improvements in Electrical Transformers
Year: 1893

page_text: Date of Application, 2nd Dec., 1893
Complete Specification Left, 2nd May, 1894-Accepted. 14th July, 1994
Improvements in Electrical Transformers.
LESLIE BRADLEY MILLER and MAURICE WALTER WOODS both of 2 Gray's
Ion Road London W.C. Electrical Engineers do hereby declare the nature of this.
invention to be as follows:-
:-
Our improvement consists in winding the secondary circuit of a ring or other
transformer with bare wire the convolutions of which are separated from one.
another by means of any suitable insulating material. On the surface of this.
secondary wire a switch, preferably formed of a number of flat strips of metal
superposed, makes a shifting contact. As the handle of the switch is turned round.
from a zero the E.M.F. of one after another of the convolutions is added to the-
secondary circuit and thus an efficient and convenient means is afforded of
regulating the current. To prevent undue heating owing to the turn or turns
immediately under the metal end of the switch being short circuited we may either
wind the secondary with brass or other wire having more resistance than copper or-
divide the switch lever into two parts joined only by a resistance.
Dated this 1st day of December 1893.
LESLIE B. MILLER.
MAURICE W. WOODS.
Improvements in Electrical Transformers.
LESLIE BRADLEY MILLER and MAURICE WALTER WOODS both of 2 Gray's.
Inn Road, London Electrical Engineers, 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 improvement consists in winding the secondary circuit of a ring or other
transformer with bare wire the convolutions of which are separated from one
another by means of any suitable insulating material. On the surface of this.
secondary wire a switch preferably formed of a number of flat strips of metal
superposed makes a shifting contact. As the handle of the switch is turned round
from a zero the E.M.F. of one after another of the convolutions is added to the:
secondary circuit and thus an efficient and convenient means of regulation is.
afforded.
In the drawings annexed
Fig. 1 is a vertical section through one of our ring transformers and
Fig. 2 a plan with the outer metal cover and the switch handle removed.
Referring to Fig. 1 A, A, is the laminated iron core of one of our ring trans--
formers, B the space in which the primary winding is wound, consisting of a number
of turns of thin wire, C the secondary winding of one layer of thick wire separated
from the primary by means of asbestos cloth and asbestos mill board, D is the:
switch which can be turned round the spindle I by means of the milled head F,
E is the core, of slate made in two halves which can be pressed together so as to.
tighten on the edge of the secondary winding by means of a nut in the base G..
In Fig. 2 some of the same parts are seen, J being the zero position of the switch.
It will be seen that the switch presses on to at least two of the secondary windings
which are consequently short circuited. By winding the secondary with brass wire,.

page_text: or other comparatively high resistance wire, instead of copper undue heating of the
turns short circuited can be avoided. Otherwise the arm of the switch may be
divided into two parts united only by a certain resistance, in a manner well known
in connection with accumulators.
Our transformer is intended to be used chiefly for heating the platinum wire
cauteries used in medical operations but the same apparatus can be employed for
adding to or diminishing the normal voltage of the electric mains in a house
or room.
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 :-
(1.) In an electrical transformer the method of regulating the electro motive
force by means of a switch which makes a sliding contact directly on to the surface
of the secondary winding.
(2.) The regulating transformer substantially as described in the Specification
and shown in the drawings Fig. 1 & Fig. 2.
LESLIE B. MILLER.
MAURICE W. WOODS.