IMPROVEMENTS IN ELECTRIC SAFETY LAMPS
Year: 1884

page_text: I THEOPHILUS COAD, of 4, South Street, Finsbury, in the county of Middlesex,
Electrician do hereby declare the nature of the said invention for "IMPROVEMENTS
IN ELECTRIC SAFETY LAMPS " to be as follows:-
This invention relates to improvements in miners' incandescent electric safety
lamps, the object of the invention being chiefly to provide means whereby on the
breakage of the casing or lantern of the lamp sparking will be prevented when the
electric current is broken and the lamp extinguished. By this arrangement danger
of explosion is prevented.
In electric safety lamps as hitherto constructed for use in mines if the globe
enclosing the filament be broken the filament will generally retain sufficient heat
to ignite carburetted hydrogen, and consequently explosion may ensue.
It has
been proposed to enclose an incandescent lamp within a glass casing or lantern
filled with water, but in this arrangement if the glass casing be broken, the
water will escape and the lamp is then practically unprotected and therefore
dangerous.
It has also been proposed to fill the outside casing with water impregnated with
carbonic acid gas under pressure for operating a flexible disc (or equivalent means)
to which is attached a contact piece in such a manner that the pressure within the
casing will cause contact to be made so as to establish the electric circuit. In this
arrangement if the casing be broken the gas and liquid contained therein will
escape, the interior pressure will be removed and the circuit will be immediately
broken and the lamp extinguished. In practice however it has been found that
the breaking of the circuit in the manner described produces a sparking which
would ignite explosive gases, so that such lamps have not been practicable.
Now my improvements consist principally in preventing such sparking by
constructing the contact pieces of sutlicient length and in placing over such contact
pieces a covering of suitable material such as india rubber or the like, which will
closely embrace the parts so as to effectually exclude all dangerous gas from coming
into contact with the sparks produced on the breaking of the electric current. And
further in order to prevent the sparking which might be produced by metallic
contact whether accidental or otherwise I dispenso with the use of terminals
by carrying the conducting liues direct from the lamp into the battery so that
when the lamp is fixed thereto, the wires will be entirely enclosed and protected.

page_text: In order to prevent the escape of the carbonic acid gas employed to produce the
pressure within the glass casing, I employ a flanged disc and a flanged ring. The
outer glass casing consists of a flanged dome, the bottom of the flange of the dome
resting against the upper face of the disc and the top of the flange bearing against
the underside of the flanged ring.
The said disc and ring are clamped together by bolts and nuts so as to allow
of securing by means of suitable packing a tight joint between the glass and
the ring and disc, thereby effectually preventing the escape of the compressed gas.
Dated this 5th day of January 188A

page_text: I THEOPHILUS COAD of 4 South Street Finsbury in the county of Middlesex
Electrician do hereby declare the nature of the said invention for "IMPROVEMENTS
IN ELECTRIC SAFETY LAMPS" 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 miners' incandescent electric safety
lamps, the object of the invention being chiefly to provide moans whereby on the
breakage of the casing or lantern of the lamp the effect of sparking will be prevented
when the electric current is broken and the lamp extinguished. By this arrange-
ment danger of explosion is prevented.
In electric safety lamps as hitherto constructed for use in mines if the globe
enclosing the filament be broken the filament will generally retain sufficient beat
to ignite carburetted hydrogen, and consequently explosion inay ensue. It has
been proposed to enclose an incandescent lamp within a glass casing or lantern
filled with water, but in this arrangement if the glass casing be broken, the
water will escape and the lamp is then practically unprotected and therefore
dangerous.
It has also been proposed to fill the outside casing with water impregnated with
carbonic acid gas under pressure for operating a flexible disc (or equivalent means)
to which is attached a contact piece in such a manner that the pressure within
the casing will cause contact to be made so as to establish the electric circuit. In
this arrangement if the casing be broken the gas and liquid contained therein
will escape, the interior pressure will be removed and the circuit will be imme-
diately broken and the lamp extinguished. In practice however it has been
found that the breaking of the circuit in the manner described produces a
sparking which would ignite explosive gases, so that such lamps have not been
practicable.
Now my improvements consist principally in preventing such sparking by
constructing the contact pieces of sufficient length and in placing over such
contact pieces a covering of suitable material such as india rubber or the like,
which will closely embrace the parts so as to effectually exclude all dangerous
gas from coming into contact with the sparks produced on the breaking of the
electric current. And further in order to prevent the sparking which might be
produced by metallic contact whether accidental or otherwise, I dispense with the
use of terminals by carrying the conducting lines direct from the lamp into the
battery so that when the lamp is fixed thereto the wires will be entirely enclosed
and protected.
In order to prevent the escape of the carbonic acid gas employed to produce the
pressure within the glass casing I employ a flanged disc and a flanged ring. Tho
outer glass casing consists of a flanged dome, the bottom of the flange of the dome
resting against the upper face of the disc and the top of the flange bearing against
the underside of the Hanged ring.
The said disc and ring are clamped together by bolts and nuts so as to
allow of securing by means of suitable packing a tight joint between the
glass and the ring and disc, thereby effectually preventing the escape of the
compressed gas.
In order to enable my invention to be fully understood I will proceed to describe
the same by reference to the accompanying drawing in which figure 1 is an
elevation and figure 2, a vertical section of an electric safety lamp constructed
according to my invention; figure 3, is a plan of the underside of the flanged disc
and figure 4 is a detached enlarged view shewing the construction of the contact
pieces. Similar letters in all the figures represent similar parts.

page_text: A is the battery and B the receptacle for the same; C the lamp, D, the flexible
disc and E, the spring for breaking contact if the lamp be broken all being of
known construction. a, and a¹, represent the contact pieces constructed as shewn
to receive the covering b, of suitable material such as india rubber or the like
which will closely embrace the contact pieces a, and a'; the lower contact piece a,
is provided with a lock nut a², for adjusting its position with regard to the upper
contact piece al; c, and c¹, are the usual conducting wires which I carry direct
from the lamp C into the battery A where they are connected direct to the poles
of the battery A as shewn at b, and b¹, instead of to the terminals usually fixed
thereto; the wires c, and c', when the lamp C is fixed thereto will be thereby
entirely enclosed and protected.
d, is the flanged disc and e, the flanged ring for fixing the outer glass f, over the
lamp C, the said glass f, being filled with water impregnated with carbonic acid
gas as heretofore; g, is the flange of the outer glass f, the bottom of the said
flange g, resting against the upper face of the flanged disc d, and the top of the
flange g, bearing against the underside of the flanged ring e; h, and i, are the bolts
and nuts for clamping the disc d, and ring e, together and j, is the packing for
securing a tight joint between the glass f, and the ring and disc.
In a lamp of this construction if the interior pressure be removed from the
flexible disc D, by the casing or glass f, becoming broken the disc D will be forced
upwards by the spring E, as shewn in figure 4, which spring E will also carry up
the contact piece a', and contact will be thereby broken between the two contact
pieces; the sparking produced by the breaking of the circuit in this manner will
be prevented from igniting the explosive gases as such gases will be effectually
excluded by the covering b, over the contact pieces u, and a. Further any
sparking which might otherwise occur is obviated by dispensing with the use of
terminals and carrying the conducting wires c, and c', direct to the battery. By
employing the flanged disc d, and ring c, and flanged outer glass f, connected
together as described the escape of the carbonic acid gas employed to produce the
pressure within the glass casing f, is effectually prevented.
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
(1) In miners' incandescent electric safety lamps the described method of
preventing the effects of sparking in the event of the breakage of the electric
circuit by enclosing the contact pieces within a covering of suitable material
substantially in the manner herein before described and represented in the accom-
panying drawing.
(2) The method of preventing sparking in miners' incandescent electric safety
lamps by carrying the conducting wires direct from the lamp into the battery
whereby they will be enclosed and protected substantially as described and
represented in the accompanying drawing.
(3) The described means for producing a tight joint to prevent the escape from
the outer glass casing of the compressed gas employed to operate the flexible dise
as herein before described and represented in the accompanying drawing.
(4). The improved miners' incandescent electric safety lamp hereinbefore
described and represented in the accompanying drawing.
G. F. REDFERN,
4, South Street, Finsbury,
Agent for the Applicant.