IMPROVEMENTS IN APPLIANCES FOR USE IN ELECTRIC LIGHTING
Year: 1886

page_text: Date of Application, 14th May., 1886.
Complete Left, 14th Feb, 1887.
Complete Accepted, 25th Mar., 1887.
I, ROBERT PERCY SELLON of 112 Belvedere Road Lambeth, S.E. do hereby declare
the nature of my invention for IMPROVEMENTS IN APPLIANCES FOR USE IN ELECTRIC
LIGHTING to be as follows:-
My Invention relates to improvements in automatic safety appliances for use in
Electric Lighting, and more especially for use where the conditions of supply of
electricity are those known as constant current" that is to say, where a current
of a certain strength is maintained constant or approximately constant in the mains,
whatever the variations of the external circuit, may be.
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"
When the current flowing in circuit, as above, is divided up among a number
of services, whether they be lamps, motors, or say a group of incandescence
lamps, so that each device of the group is absorbing a due amount of current, it
follows that if one or more of such devices on a single group be intentionally or
accidentally thrown out of circuit, the current will divide itself among those
remaining in circuit possibly to their injury or destruction and this may result in a-
fracture of the whole circuit at that point.
My Invention has for its object to provide means to obviate the occurrence of
this fault.
I attain my object, as follows :-
I provide one or more magnets or solenoids which, upon the passage of a
predetermined amount of current, attract an armature or core, which armature or core
may interpose into the circuit or cause to be interposed into the circuit a sufficient
amount of resistance or a sufficient number of additional devices, such as incandescence
lamps, as to prevent injury to those previously remaining in circuit; and restoring
the, if desired, to their normal condition of working.
Should this interposition of additional resistance or devices fail to restore the group
to a normal or safe condition of working, and should an excess of current again flow
through the devices in circuit, the aforesaid magnets or solenoids or other magnets or
solenoids may by attracting an armature or core short circuit, or cause to be short
circuited, the whole of the devices comprising the group.
I prefer the following method of carrying out my Invention. I provide two electro-
magnets, the first, which I will call magnet "A" being wound with comparatively

page_text: high resistance wire placed across the group of devices, as a shunt: the second, which
I will call magnet "B" is also wound with comparatively high resistance wire, placed
as a shunt across the group of devices; "B" magnet is also partially wound with
wire capable of conveying the current, and "A" magnet may in some cases be wound
with a comparatively coarse wire capable of conveying the current which circulates in
the additional devices thrown into circuit by the magnet "A."
Now under normal conditions of working a certain amount of current traverses the
magnets "A" and "B" and excites them, the current passing in the magnets being
determined by the electromotive force at the terminals of the group.
Now, if some of the devices in the group are accidentally or intentionally thrown
out of circuit of greater current than the normal will traverse each member of
the remaining devices and the electromotive force at the terminals of the group will
be raised thus the magnetic strength of the magnets "A" & "B" will be increased,
and by suitable adjustment the magnet "A" at the proper time will attract an
armature core, by means of which additional safety devices such as resistance or
incandescence lamps will be thrown into the circuit of the group, and the current
traversing each member of the group be restored to a normal or safe limit :-the
coarse wire, if wound on "A," will assist in holding up the armature in place, until
such time as a replacal into circuit of further useful devices in the group diminishes
the magnetising strength of the magnet "A," when the armature core will be
automatically released, the additional safety devices be thrown out of circuit and the
normal operation of the group continue. In some cases the coarse wire upon the
magnet "A may be omitted.
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Now, should an excess of current, which the magnet "A is not sufficient to
provide for, traverse the members of the group, or should the whole of the members of
the group be destroyed or otherwise thrown out of circuit, thus tending to fracture the
whole circuit at that point, then the magnet "B" will become strongly magnetised,
and by suitable adjustment will attract an armature core, which will establish a "short
circuit at that point, the armature core being held in place by the consequent
circulation of current through the coarse wire coils upon the magnet "B." Thus
fracture of the circuit will be obviated. The coarse wire coils may be made of such a
resistance or such an equivalent resistance may be inserted at that point into the main
circuit, that upon a restoration of the group into its normal condition, the magnet "B"
may release its armature, when the current will traverse the group.
In order to always maintain surfaces of good contact, such that there shall be no
liability to derangement of this appliance owing to the contact surfaces becoming
oxydised by sparks, I provide that the armature or armatures, when attracted by the
solenoids, shall cause two contacts to be made, one being made on attraction ensuing
and broken on attraction of the armature ceasing slightly before the other, in such a
way that the current shall have two paths offered to it, when contact is fully made,
the sparking occurring, however, always at one of the two contacts, thus at all times
ensuring a sufficient contact at the other of the two.
Dated this 14th day of May 1886

page_text: COMPLETE SPECIFICATION.
Improvements in Appliances for Use in Electric Lighting.
I, ROBERT PERCY SELLON of Victoria Works, 112, Belvedere Road, Lambeth, in
the County of Surrey, Electrical Engineer, 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 Improvements in automatic safety appliances for use in
electric lighting, and more especially for use where the conditions of supply of
electricity are those known as constant current, that is to say, where a current of a
certain strength is maintained constant or approximately constant in the mains,
whatever the variations of the external circuit may be.
When the current flowing in curcuit, as above, is divided up among a number of
services, whether they be are lamps, motors or say a group of incandescence lamps,
so that each device of the group is absorbing a due amount of current, it follows that
if one or more of such devices on a single group be intentionally or accidentally
thrown out of circuit,t he current will divide itself among those remaining in circuit,
possibly to their injury or destruction and this may result in a fracture of the whole
circuit at that point.
My Invention has for its object to provide means to obviate the occurrence of this
fault.
I attain my object, as follows:—
I provide one or more magnets or solenoids which, upon the passage of a
predetermined amount of current, attract an armature or cove, which armature or cove
may interpose into the circuit or cause to be interposed into the circuit a sufficient
amount of resistance or a sufficient number of additional devices, such as incandescence
lamps, as to prevent injury to those previously remaining in circuit; and restoring
them, if desired, to their normal condition of working.
Should this interposition of additional resistance or devices fail to restore the group
to a norinal or safe condition of working or should an excess of current again flow
through the devices in circuit, the aforesaid magnets or solenoids or other magnets or
solenoids may, by attracting an armature or core short circuit or cause to be short
circuited, the whole of the devices comprising the group.
The accompanying drawings clearly illustrate one method of carrying this Invention
into effect.
M. is an electro magnet wound partly with fine wire shewn at F, which is
connected on a shunt with the terminals of the group and partly with coarse wire,
shewn at C, which is wound in series with the group.
When a normal current is passing and dividing itself among the group say of
incandescence lamps shewn at G, the armatures A & A' are out of contact with the
contact pieces P&P.
Supposing some of the lamps comprising the group "G" to be thrown out of
circuit, then the current will divide itself among a smaller number of lamps and an

page_text: increase of electro motive force at the terminals T. T¹ will ensue thus more strongly
magnetising the magnet "M" through the fine wire and attracting the armature A
into contact with the contact piece P. this closes the circuit of one or more additional
devices D and so reduces the current passing through the incandescence lamps,
composing the group G. So soon as the electromotive force at the terminals T. T' is
again reduced to the normal, the armature A automatically falls out of contact with
the contact piece P.
Now, should a greater excess of current tend to flow through the group, than the
action of the armature A and the group D can compensate for, then the magnet. M
becomes more highly magnetised and attracts the armature A¹ into contact with the
contact piece P, thus establishing a safety circuit across the terminals in this circuit
is included the coarse wire upon the magnet. M; and the current circulating
through this continues to magnetise the magnet M, thus holding the armature A¹ in
contact with the contact piece P, until the normal state of things is re-established.
The armatures A & A¹, in rising bring the intermediate contact pieces S & S¹ into
contact both with themselves and the contact pieces P. P¹ in this way one contact
surface on either side of the magnet M is maintained free from oxidation by sparking.
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 :-
(i) The automatic safety device, substantially as hereinbefore described and
illustrated.
(ii) The combination of a magnet or magnets wound with two circuits, with an
armature or armatures, and devices to prevent the oxidation of surfaces by sparking,
all substantially as and for the purposes hereinbefore described.
Dated this 14th day of February 1887.