Year: 1888

page_text: I, KILLINGWORTH WILLIAM HEDGES of 25 Queen Anne's Gate. Westminster in
the County of Middlesex, Civil Engineer do hereby declare the nature of my said
invention to be as follows:
Whereas in order to render transformers or induction coils, perfectly safe, when
employed by the distribution of the electric light or power, it is necessary to avoid
leakage between the primary and secondary coils. For effecting this
devices
purpose
have been used which cause the disconnection of the primary circuit from the mains,
when any point of the secondary circuit acquires a certain potential above that of the
earth. One of such devices consists of a fusible wire, connected with the secondary
circuit, which sustains a metallic disc a short distance above another disc connected
with the earth. A piece of foil placed between the two discs forms the connection,
by static attraction, and allows the leakage current to escape to earth.
Now the object of my invention is to effect improvements in apparatus of the
description above referred to.
In carrying out my invention, I dispense with the foil placed between the discs as
above mentioned, and connect the secondary circuit to an electrode fixed in a tube or
receiver made of glass or other suitable insulating material, the tube containing
rarefied gas. Another electrode is also fixed in the tube and connected to earth.
Or on either side of the tube 1 place a fuse wire, which, on melting, may be
made to establish a connection between the poles of the primary circuit, with the
object of short circuiting them, and thus causing the main fuse or cut out on the
primary circuit to melt.
In another arrangement the fuse wire on the secondary circuit, between the tube
containing the rarefied gases and the earth, or between the tube and the secondary
coil, may be dispensed with, and a magnetic device substituted therefor with the
same object viz-of opening the primary circuit direct, or by short circuiting the
poles, causing the cut out protecting it to melt.
Rarefied gases are found to be moderately good conductors but there is a large
resistance at the surface of contact between the attenuated gas and the metal
conductor

page_text: In order to facilitate the passage of the electricity, I sometimes form my electrodes
as points, as I form them in such a manner as to offer the least resistance; their
distance apart being fixed according to the potential at which it is required that
the leakage current shall pass; this distance being also effected by the degree of
rarefaction of the gas in the tube.
I also sometimes apply my invention to the metal plate of those transformers
in which the primary circuit is separated from the secondary, by means of a plate
of metal which is connected to earth.
I also sometimes apply my invention to the protection of any part of an electric
circuit, namely, either to the dynamos, conductors or fittings, so as to prevent the
difference of potential of any part of the circuit and the earth exceeding a certain
amount.
If it is required to alter the distance between the electrodes in the sealed tube
contained the rarefied gas, I effect the same by making the ends of one or both of
the electrodes loose and of any metal which is influenced by a powerful magnet, or a
solenoid coil placed outside the tube.-The movable end of the electrode may be
adjusted or caused to slide up and down, by the action of the powerful magnet or
solenoid coil outside the tube.
My invention may also be applied to the protection of any part of an electric
circuit from lightning in that leakage will take place through the tube containing the
rarefied gas to earth if the potential of the circuit increases more than a determined
amount.

page_text: Improvements in Electrical Safety Appliances.
I KILLINGWORTH WILLIAM HEDGES, of 25 Queen Anne's Gate Westminster, in the
County of Middlesex, Civil Engineer, do hereby declare the nature of my said
invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
Whereas in order to render transformers, or induction coils, perfectly safe, when
employed for the distribution of the electric light or power, it is necessary to avoid
leakage between the primary and secondary coils.
For effecting this purpose devices have been used which cause the disconnection of
the primary circuit from the mains when any point of the secondary circuit acquires
a certain potential above that of the earth. One of such devices consists of a fusible
wire connected with the secondary circuit, which sustains a metallic disc, a short
distance above another disc connected with the earth. A piece of foil placed between
the two discs forms the connection by static attraction, and allows the leakage current
to escape to earth.
Now the object of my' invention is to effect improvements in apparatus of the
description above referred to.
In carrying out my invention I connect the secondary circuit to an electrode fixed
in a tube or receiver made of glass or other suitable insulating material, the tube
containing rarefied gas. Another electrode is also fixed in the tube and connected
to earth.
An ordinary incandescent lamp which has its filament broken in such a manner
that the two ends spring a short distance apart owing to the resilience of the filament,
may be employed as the receiver, if the electro motive force of the circuit to earth is
sufficiently high, but it is preferable to partially destroy the vacuum in the lamp so
as to diminish the resistance to the passage of the spark. If so preferred the two
electrodes in the Receiver may be placed parallel to each other, and the ends of each
or both fitted with a projection from which the sparks will pass.
On either side of the tube I place a fuse wire, which on melting may be made to
establish a connection between the poles of the primary circuit, with the object of
short circuiting them, and thus causing the main fuse, or cut-out, on the primary
circuit to melt.
In another arrangement the fuse wire on the secondary circuit, between the tube
containing the rarefied gases, and the earth, or between the tube and the secondary
coil, may be dispensed with, and a magnetic device substituted therefor, with the same
object, vict. of opening the primary circuit direct, or by short-circuiting the poles,
causing the cutout protecting it to melt.
Rarefied gases are found to be moderately good conductors, but there is a large
resistance at the surface of contact between the attenuated gas and the inetal
conductor.

page_text: In order to facilitate the passage of the electricity, I sometimes form my electrodes
as points, or form them in such a manner as to offer the least resistance: their
distance apart being fixed according to the potential at which it is required that the
leakage current shall pass: this distance being also affected by the degree of
rarefaction of the gas in the tube.
I also sometimes apply my invention to the metal plate of those transformers in
which the primary circuit is separated from the secondary by means of a plate of
metal which is connected to earth.
I also sometimes apply my invention to the protection of any part of an electric
circuit, namely, either to the dynamos, conductors, or fittings, so as to prevent the
difference of potential of any part of the circuit, and the earth exceeding a certain
amount.
If it is required to alter the distance between the electrodes in the sealed tube
containing the rarefied gas, I effect the same by making the ends of one or both of
the electrodes loose, and of any metal which is influenced by a powerful magnet, or
a solenoid coil placed outside the tube.
The moveable end of the electrode may be adjusted or caused to slide up and down
by the action of the powerful magnet or solenoid outside the tube, or I may make the
electrodes adjustable in any other convenient manner.
And in order that my said invention may be particularly described and ascertained
reference is hereby made to the accompanying drawings.
Fig. 1 is a side view of the tube or receiver made of glass, or other insulating
material, according to my invention, and containing rarefied gas and into which are
fixed two electrodes marked A and A¹. These are fastened to two metal caps or
terminals marked B and B to which electrical connection is made.
Fig. 2 is a view of the arrangement for breaking the primary by means of a fuse
wire or foil marked A which is firmly clamped by the clips marked B and C. The
action is as follows:-on a current passing from the Receiver through the wire L' to
earth the fuse A will melt and cause the weight D which is suspended on A to drop,
thus either opening a switch as shewn by S Fig. 2, which will break the primary
circuit or by short circuiting the two poles of the transformer the main fuse or cut out
will be melted and the primary circuit opened.
Fig. 3 shows a side view of a magnetic device which on the current passing through
the receiver and the wire L' causes the armature A to be attracted thus releasing
the arm B by the action of the weight C and opening the circuit at the connecting
block D.
Figs. 4 and 5, are a side and front view of another magnetic device for automatically
short circuiting the primary circuit and thus causing the main fuse or cut out to be
melted. The portion marked A is an armature which is attracted by the electro
magnet M M but which can be held if required in position as shown by the safety
catch marked B releasing the bar marked C which on falling makes contact on the
contacts D and D' which are in connection with the primary poles of the
transformer.
The bar is guided by the rods F and G and tripped by hook F¹ being released
by pressure against the pin F².
The arrangement is shown diagramatically by Fig. 6 in which A is the receiver
connected to the circuit on which the lamps are fixed. B is the magnetic device,
E the earth; D and D¹ are the terminals connected to the two poles of the trans-
former T, which is connected with the primary leads L and L. F and F¹ are the
safety fuses which will be melted on the short circuiting of D and D¹.
Fig. 7 shows an arrangement for bringing one of the electrodes on the receiver
nearer to the other for the purpose of regulating the electrical pressure at which the
excess leakage current to earth shall take place.
A is a glass tube forming the receiver.
On the electrode B an iron socket
or shield is fitted by springs or other means sufficiently firmly to prevent its
falling.

page_text: When it is intended to move the iron socket a powerful magnet is applied outside
the glass so as to overcome the friction by which it holds to the electrode and cause
it to approach or recede from the other electrode D, or the distances between the .
electrodes may be varied in any other convenient manner.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim as new is :.
I. The use of Receivers A in combination with transformers or their equivalents
for the purpose of putting in motion by means of a diverted current through the
receivers of safety apparatus as soon as or before the current in the secondary circuit
has reached a dangerously high tension, substantially as described and shown on the
drawings annexed hereto.
II. The method of liberating the short circuiting piece C by means of a tripping
apparatus substantially as described and shown in Figs. 4 and 5.
III. Constructing receivers for use in manner described in claim I with adjustable
electrodes.
IV. The general combination and arrangement of parts together forming my
improvements in Electrical safety appliances substantially as herein described.
Datod 93d November 1888
GEO. DOWNING,
Agent for Applicant.