IMPROVE- MENTS IN ELECTRIC SAFETY LAMPS
Year: 1886

page_text: Date of Application, 11th Nov., 1886
Complete Left, 9th Aug., 1887.
Complete Accepted, 9th Sept., 1887.
I, ANDREW HOWAT of 65 Bristol Street Hulme, Manchester in the County of
Lancaster, Engineer, do hereby declare the nature of said Invention for IMPROVE-
MENTS IN ELECTRIC SAFETY LAMPS to be as follows:-
--
My invention relates to improvements in Electric Safety Lamps and has for its
principal object to provide means for instantaneously extinguishing the light in the
event of certain irregularities occurring as hereinafter described.
In carrying out my Invention I mount the incandescent lamp on a stand or holder
and connect the platinum wire terminals to the wires of an electric battery, the
circuit being completed or broken at will by means of a switch or lever.
I surround the lamp globe with a strong glass dome or globe and secure it firmly
to the stand or holder taking care to make an air tight joint between the dome and
the stand in such manner that a chamber or air space is formed around the lamp
globe.
The stand or holder is provided with a pipe or passage which communicates with
the chamber and is controlled by a valve and there is also a hole or opening in the
stand which is covered by a diaphragm of india rubber or other suitable air tight and
yielding material so arranged that when pressed outward it will operate the switch
lever and complete the circuit.
When the lamp is to be used I connect the passage leading into the chamber to a
pump and force air into the space between the globe and the dome until the air is
sufficiently compressed to force the flexible diaphragm outward thereby operating the
switch-lever completing the electric circuit and lighting the lamp.

page_text: In the event of the dome getting broken or any leakage of air taking place the
tension on the diaphragm is at once relaxed and as it résumes its normal position the
switch lever moves thereby breaking the electric circuit and extinguishing the light.
In case the inner globe is broken as well as the dome the compressed air expanding
will extinguish the light before any explosive gas can reach it.
The lamp is or may be locked by means of a cap and lead rivet or in other
convenient manner in order to prevent the lamp being tampered with by any
unauthorised person.
Dated this 10th day of November 1886.
H. B. BARLOW,
Agent.
COMPLETE SPECIFICATION.
Improvements in Electric Safety Lamps.
I ANDREW HOWAT of 65 Bristol Street Hulme Manchester in the County of
Lancaster Engineer, do hereby declare the nature of said Invention for IMPROVE-
MENTS 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 :-
My invention relates to improvements in electric safety lamps and has for its
principal object to provide means for instantaneously extinguishing the light in the
event of certain irregularities occurring as hereinafter described.
In carrying out my Invention I mount the incandescent lamp globe on a stand or
holder and connect the platinum wire terminals to the wires of an electric battery the
circuit being completed or broken by means of a switch or lever.
I surround the lamp globe with a strong glass dome or globe and secure it firmly
to the stand or holder taking care to make an airtight joint between the dome and
the stand in such manner that a chamber or air space is formed around the lamp globe.
The stand or holder is provided with a pipe or passage which communicates with
the chamber and is controlled by a valve and there is also a hole or opening in the
stand which is covered by a diaphragm of indiarubber or other suitable airtight and
yielding material so arranged that when pressed outward it will operate the switch
lever and complete the circuit.
When the lamp is to be used I connect the passage leading into the chamber to a
pump and force air into the space between the globe and the dome until the air is
sufficiently compressed to force the flexible diaphragm outward thereby operating the
switch lever completing the electric circuit and lighting the lamp.

page_text: In the event of the dome getting broken or any leakage of air taking place the
tension on the diaphragm is at once relaxed and as it resumes its normal position the
switch lever moves thereby breaking the electric circuit and extinguishing the light.
In case the inner globe is broken as well as the dome the compressed air expanding
will extinguish the light before any explosive gas can reach it.
The lamp is or may be locked by means of a cap and lead rivet or in other
convenient manner in order to prevent the lamp being tampered with by any
unauthorized person.
And in order that my Invention may be fully understood and readily carried into
effect I will describe the accompanying two Sheets of Drawings reference being had
to the figures and letters marked thereon.
Figure 1 is an elevation of an electric safety lamp made according to my Invention.
Figure 2 is an elevation of the lamp with the lower part of the casing removed.
Figure 3 is a plan of the underside and Figure 4 a plan of the upperside of the
lamp stand or holder.
Figures 5, 6 and 7 are detail views of the lower part of the casing.
Similar letters refer to similar parts throughout the several views.
The incandescent lamp globe a is mounted on a spiral spring 6 connected to a stand
or holder c or any other suitable mode of mounting the globe a may be adopted.
One of the platinum wiro terminals is connected to a wire d the other terminal is
connected when the lamp is working by a switch lever e to a wire d' both the wires d
and d¹ being connected to an electric battery. The holder c has on the upper side an
annular plate or ring f secured to it by screws f¹ and upon this ring is mounted the
glass dome g attached to the ring by a ring and screws h¹. The lower side of the
holder c is covered by a casing i attached to it by screws not shown passing through
holes in the casing i or other suitable means and the casing i has a handle j pivoted
to it by which the lamp may be carried or suspended in any position.
To prevent the lamp being tampered with any convenient arrangement may be
employed for locking the parts of the lamp together such as a swivel on the upper
part connected by a lead rivet to an eye or projection on the casing i.
Leading from the interior of the dome g through the holder e is a passage c¹ which
is kept normally closed by a valve k controlled by a spring : this passage c¹
communicates with the exterior of the lamp through a pipe c² which passes through a
slot in the casing i and is closed by a screwed cap c³. By removing the cap c³ and
connecting the pipe c² to an air pump the interior of the lamp i.e. the space between
the dome g and globe a may be filled with compressed air.
The connecting wire d' is attached by a nut to a pin or spindle contained in a
hollow projection ct on the underside of the holder c and there is a spiral spring " on
the pin which keeps the latter normally out of contact with the switch lever e.
A hole is bored in the holder c into the hollow projection c* and this hole is covered
by a disc of indiarubber or other suitable airtight and yielding material m. When
the space between the dome g and the globe a is filled with compressed air as described
the disc m is forced against the head of the pin thereby overcoming the resistance of
the spring and completing the electric circuit and lighting the lamp by moving the
pinto which the wire d' is attached into contact with the switch lever e.
The slotted portion of the casing i through which the wires d d¹ pass is composed
of ebonite or other suitable insulating material.
The lamp will be at once extinguished when the pressure of air on the disc m is
reduced through leakage of air taking place and it is therefore important that care
should be taken to make good airtight joints between the dome and the holder and
between the other parts of the lamp.
The lamp will of course be immediately and automatically extinguished in the event
of the glass dome g being broken and the disc m being relieved of the pressure of air
on it and in case the lamp globe a be broken also the compressed air as it expands
will extinguish the light before any explosive gas can reach it. The lamp may also be
extinguished at will without either opening the casing or disconnecting the wires d d¹
rom the battery but by simply inserting a key through an opening made for the

page_text: purpose in the casing i and with it turning the spindle of a valve arranged to
control a hole or passage in the holder c the valve can be opened to allow the
compressed air within the dome g to escape through the passage c' thereby reducing
the pressure on the disc m and extinguishing the lamp.
Having now particularly described and ascertained the nature of my said Invention
and in what manner the same is to be performed I would have it clearly understood
that I do not limit myself to the exact details of construction or the arrangement of
the parts as herein shown and described as the same may be varied or modified
without departing from the nature of my Invention and I declare that what I
claim is―
1. The combination with an incandescent lamp globe mounted on a suitable stand
or holder and enclosed in an outer glass dome or globe of a yielding or flexible disc
or diaphragm so arranged that the pressure of the air contained in the space between
the lamp globe and dome acting thereon forces the said disc outward and operates
means whereby an electric circuit is completed and the lamp is lighted and vice versa
when the pressure of air on the said disc is lost or sufficiently reduced the electric
circuit is broken and the lamp extinguished substantially in the manner and for the
purposes herein described and as illustrated by the Drawings.
2. The combination with the incandescent lamp globe a the glass dome g and the
between
holder c provided with a passage for the supply of compressed air to the space
the lamp globe a and the dome g said passage being kept normally closed by a valve
to prevent the return of air through said holder of the flexible or yielding disc m and
the means shown and described or any suitable equivalent for completing an electric
circuit and lighting the lamp or breaking the circuit and extinguishing the lamp
substantially as and for the purposes specified.
3. The construction combination and arrangement of parts constituting my
improved electric safety lamp substantially as and for the purposes herein described
and as shown.
Dated this 8th day of Anonst 1887
H. B. BARLOW,
17, St. Ann's Square, Manchester,
Agent for Applicant.