IMPROVEMENTS IN BREAKING ELECTRIC CONTACT TO PREVENT OVERHEATING BY IMPERFECT CONTACT
Year: 1884

page_text: PROVISIONAL SPECIFICATION.
1, Sir WILLIAM THOMSON, Knight of Glasgow College, Doctor of Laws and
Professor of Natural Philosophy in the University and College of Glasgow in the
County of Lanark, North Britain do hereby declare the nature of the said
invention for " IMPROVEMENTS IN BREAKING ELECTRIC CONTACT TO PREVENT
OVERHEATING BY IMPERFECT CONTACT" to be as follows:-
This Invention relates to improvements in breaking electric contact to prevent
overheating by imperfect contact, that is to say, through the contact being
imperfectly made or imperfectly broken in a tap or switch for electric light I use
an appliance in which gravity takes the place of the spring generally used hitherto.
For this purpose I employ a plunger consisting of a stout straight wire capable
of moving up and down through a sufficient range through two guide ringa
metallically connected with one part of the circuit to be made and broken.
A spring or springy piece connected with the other part of the circuit is pressed
up by the upper end of the plunger when the plunger is pushed up. The mutual
pressure between the spring and the plunger gives rise to horizontal forces on the
two guide rings, and the plunger is held up by virtue of the friction due to these
three forces resisting its downward motion. When the plunger is pulled down so
as to press too lightly on the spring to bear its weight, it falls away of itself, it
being quite free to fall down through the guide rings until stopped by a pin which
prevents it falling out. The arrangement may be varied with advantage in some
places by attaching the spring to the plunger, and letting the part of the circuit, on
which the head of the plunger presses, be rigid. This modification is chiefly
convenient for a two-way tap or a multiple tap.
For this appliance, I make the plunger tubular with its upper end open, with a
stout steel or other springy enough wire fixed on the bottom of the tube and
projecting above the top. On the opper end of this wire a metal ball is fixed, by
which the contacts are made on pieces of metal fixed at different places along the
range of motion. If the plunger is pulled down so as to be let fall from one of
the contact pieces, it, makes contact on the piece below it, until pulled down so as
to leave the lowest of the contact pieces, when it falls off and breaks contact
altogether, being held by a pin from tumbling out of its guide rings.

page_text: COMPLETE SPECIFICATION.
I, Sir WILLIAM THOMSON Knight, of Glasgow College, Doctor of Laws and
Professor of Natural Philosophy in the University and College of Glasgow, in the
County of Lanark, North Britain, do hereby declare the nature of my invention
for "IMPROVEMENTS IN BREAKING ELECTRIC CONTACT TO PREVENT OVERHEATING
BY IMPERFECT CONTACT" and in what manner the same is to be performed, to
be particularly described and ascertained in and by the following statement:-
This Invention relates to improvements in breaking electric contact to prevent
overheating by imperfect contact, that is to say, through the contact being
imperfectly made or imperfectly broken.-In a tap or switch for electric light, I use
an appliance in which gravity takes the place of the spring generally used
hitherto. For this purpose I employ a plunger consisting of a stout straight wire
capable of moving up and down through a sufficient range through two guide
rings metallically connected with one part of the circuit to be made and broken.-
A spring or springy piece connected with the other part of the circuit is pressed up
by the upper end of the plunger when the plunger is pushed up.-The mutual
pressure between the spring and the plunger gives rise to horizontal forces on the
two guide rings and the plunger is held up by virtue of the friction due to these
three forces resisting its downward motion.-When the plunger is pulled down so
as to press too lightly on the spring to bear its weight, it falls away of itself, it
being quite free to fall down through the guide rings until stopped by a pin which
prevents it falling-out-The-arrangement-inay-be-varied with advantage in some
places by attaching the spring to the plunger, and letting the part of the circuit,
on which the head of the plunger presses, be rigid.-This modification is chiefly
convenient for a two-way tap or a multiple tap.
For this appliance, I make the plunger tubular with its upper end open, with a
stout steel or other springy enough wire fixed on the bottom of the tube
and projecting above the top.--On the upper end of this wire a metal ball is fixed,
by which the contacts are made on pieces of metal fixed at different places along
the range of motion. If the plunger is pulled down so as to be let fall from one
of the contact pieces, it makes contact on the piece below it, until pulled down so
as to leave the lowest of the contact pieces, when it falls off and breaks contact
altogether, being held by a pin from tumbling out of its guide rings.
In order that my said Invention may be most fully understood and readily
carried into effect, I will proceed to describe the Drawings hereunto annexed.
In applying my present Invention for practical use, I prefer to describe it as used
in combination with a very convenient bracket support for an incandescent lamp
together with its mode of connection to the conducting wires of an electric-light
system; and wherein the bracket bearing the lamp and shade or globe, if such is
used, and the make and break arrangement constituting my Invention is rendered
portable as represented at Figures 1, and 2, which are respectively a side elevation
and a longitudinal section of such portable bracket with my present Invention
shewn applied thereto.-Such portable bracket, which however forms no part
of my present Invention, is available for giving light at various points in a room or
in different rooms wherever a bracket connection may be placed.-The bracket
connection for this purpose is constituted by two rings a, and b, insulated
from each other and fixed one above the other ou a plate c, of insulating material,
such as wood, so as to form the upper and lower ends of a vertical space or socket;
these two fixed rings being connected to the two sides of a break in one
of the two conductors leading to the bracket connection so constituted.-The end
of the bracket d, next the wall is of a form suitable to fit easily into and rest
in the two rings a, and b.-The part e, fitting into the ring a, is formed
of metal continuous with the metal of the bracket itself, while the part fitting
into the ring, consists of an insulated metallic ring f, secured to the bracket

page_text: by a block or tube g, of insulating material.-These two metallic surfaces e, and f,
are so placed as to make contact with the upper ring a, and the lower ring b, when
the bracket is placed in position, so as to be supported by them, and I may make
the block c, of insulating material, hollow as shewn in the accompanying Drawings,
so as to enclose a switch for making and breaking the current for the lamp.-
Proper stops are placed where necessary for safety against accidental forces tending
to lift up the bracket, or to slue it to one side or the other, and so risk breaking the
lamp or its shade or globe.
To prevent overheating through the contact being imperfectly made or imper-
fectly broken in a tap or switch for electric light, I use an appliance illustrated at
Figures 1, and 2, in which gravity takes the place of the spring generally
used hitherto. For this purpose, I use the plunger consisting of the stout straight
wire h, capable of moving up and down through a sufficient range through
two guide rings i, and j, metallically connected with one part of the circuit to be
made and broken.-The spring k, connected with the other part of the circuit is
pressed by the upper end of the plunger h, when the said plunger is pushed up.-
The mutual pressure between the spring k, and the plunger h, gives rise to
horizontal forces in the two guide rings i, and j, and the plunger h, is held
up by virtue of the friction due to these three forces resisting its downward
motion. When the plunger h, is pulled down so as to press too lightly on
the spring k, to bear its weight, it falls down of itself into the position shewn on
the accompanying Drawings, it being quite free to fall down through tho
guide rings i, and j, until stopped by a pin l, which prevents it falling out.-The
arrangement may be varied with advantage in some places by attaching a spring to
the plunger, and letting the part of the circuit, on which the head of the plunger
presses, be rigid.
The form or arrangement of my Invention chiefly convenient for a two-way
or a multiple tap is illustrated at Figures 3, to 6, (inclusive) of the accompanying
Drawings. These Figures represent the said multiple tap respectively in front
elevation, plan, and in vertical and horizontal sections taken respectively on the
lines A. B., Figures 4, and 6, and C. D., Figure 3.
The plunger h, is tubular with its upper end open, and with a steel or other
springy enough wire m, fixed in the tube and projecting above its top.-On the
upper end of this wire m, the metal ball n, is fixed, by which the contacts are made
on the pieces of metal o and p, fixed at different places along the range of motion.-
If the plunger is pulled down so as to be let fall from the contact piece p, it makes
contact on the piece o, below it, until pulled down so as to leave the lower of the
contact pieces, when it falls off and breaks contact altogether, (in which position it
is represented upon the accompanying Drawings), being held by a collar 9, from
falling out of its guide rings 7, and 8.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is:-
First. The switch for making and breaking contact for electric lamps either of
the arc or incandescent type substantially as hereinbefore described with reference
to Figures and 2, of the accompanying Drawings.
Second. The multiple tap or switch for electric circuits substantially as herein-
before described with reference to Figures 3, to 6, (inclusive) of the accompanying
Drawings.
Dated thin