Improvements in Electric Systems and Apparatus.
Year: 1893

page_text: Date of Application, 22nd Nov., 1893
Complete Specification Left, 21st Aug., 1894-Accepted, 22nd Sept., 1894
PROVISIONAL SPECIFICATION.
Improvements in Electric Systems and Apparatus.
We, PERCY EDWARD POWNALL of " Carlton," Blenheim Gardens, Willesden
Green, in the County of Middlesex, Electrical Engineer, and ROBERT BOLGER
POWNALL of 73 Queen Victoria Street, in the City of London, Engineer, do
hereby declare the nature of this invention to be as follows:-
This invention relates more particularly to electric systems and apparatus to be
employed in mines, but the invention may also be used in any place in which it is
desired to automatically switch off the current should "sparking" in the open take
place. Owing to the liability of an electric spark firing the gas that may be in
a mine electricity is now rarely or never employed in mines in which explosive gas
is present.
By the use of this invention electricity may however be freely employed in
mines of all characters. To this end it is proposed to encase all parts of the
apparatus which are in the mine and at which "sparking" could take place, and
to maintain in such casing a constant air pressure, any serious fall of such pressure
(owing say to the uncovering or breaking of the casing) being caused to break
electrical contact and switch off the entire current from the mine.
Several arrangements of apparatus may be made for carrying out this system
of automatically breaking circuit but it is judged that the following will be both
efficacious and economical.
The electric conductors are carried in pipes connected to the motors. switches,
resistances, and lamps or other electrical apparatus in the mine, such apparatus
being enclosed in air-tight boxes, or if preferred the electrical conductors may be
buried or otherwise encased and their pipes simply lead to and from the apparatus
boxes. A current of air is forced down the intake pipe and after passing through
the boxes travels up the return pipe to a nozzle or other opening by which the
discharge and consequently the pressure in the pipes and boxes can be governed.
The pressure in the pipes is also exerted on a water gauge carrying a float
connected to an electric switch which may consist of a bridge piece which on
rising or falling will break or make circuit through mercury cups arranged in a
circuit with electro magnets which hold or release the main switches depending
upon whether the circuit through the cups is maintained or not.
The main switches preferably have an armature or iron lever pivoted at one end
and on the same centre therewith but separate therefrom is a switch arm or lever
which when raised will electrically connect two contacts and so complete the
main circuit. When the switch arm is raised so as to make electrical connection
with the two contacts, a catch or pawl will engage with a projection on the switch
arm and so hold the said arm in position. On the armature will be a projection
or cam which when the armature drops will push on one side the catch or pawl
and cause it to disengage from the projection on the switch arm, and the switch
arm will then drop. A spring may be arranged to force the switch arm away from
the contact, the remainder of the drop being caused by gravity. A handle may
be fixed to the armature to raise it into position, and there may be a projection
on the armature which projects under the switch arm, so that when the armature
s raised into position the switch arm is also raised into position, so that there is
little likelihood of the switch arm being raised without raising the armature.

page_text: It will be seen that according to this invention the whole of the electrical
apparatus is contained in fresh air forced in from the surface, and if by any
accident or negligence any of the pipes, tubes, cases or boxes should be broken
or the covers removed so that there is danger of the electrical apparatus coming
in contact with the gases in the mine, the electrical circuit will immediately be
broken and the electrical current stopped owing to the air escaping at the break,
and consequently the air pressure falling at the point where the make and break
apparatus is actuated, fresh air at the time being provided from the surface at the
point of fracture. If preferred air may be forced through both pipes or both
the electrical conductors contained in one pipe and the air forced through it.
The automatic cut out apparatus in these cases is placed down the mine and
encased with the other electrical apparatus.
Dated the 22nd day of November 1893.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London, Chartered Patent Agent,
For the Applicants.
COMPLETE SPECIFICATION.
Improvements in Electric Systems and Apparatus.
We, PERCY EDWARD POWNALL of "Carlton," Blenheim Gardens, Willesden
Green, in the County of Middlesex, Electrical Engineer, and ROBERT BOLGER
POWNALL of 73 Queen Victoria Street in the City of London, Engineer, do
hereby declare the nature of this invention and in what mauner the same is to
be performed, to be particularly described and ascertained in and by the following
statement :-
This invention relates more particularly to electric systems and apparatus to be
employed in mines, but the invention may also be used in any place in which it is
desired to automatically switch off the current should "sparking" in the open take
place. Owing to the liability of an electric spark firing the gas that may be in
a mine electricity is now rarely or never employed in mines in which explosive gas
is present.
By the use of this invention electricity may however be freely employed in
mines of all characters. To this end it is proposed to encase all parts of the
apparatus which are in the mine and at which "sparking" could take place, and
to maintain in such casing a constant air pressure, any serious fall of such pressure
(owing say to the uncovering or breaking of the casing) being caused to break
electrical contact and switch off the entire current from the mine or where the
switches are placed in the mine and branch circuits are employed then to switch it
off from any particular branch.
Several arrangements of apparatus may be made for carrying out this system
of automatically breaking circuit but it is judged that the arrangement hereinafter
described will be both efficacious and economical and to enable it to be clearly
understood reference is made to the accompanying drawings.
The electric conductors are carried in pipes a b connected to the motors,
switches, resistances, and lamps c or other electrical apparatus in the mine, such
apparatus being enclosed in air-tight boxes, or if preferred the electrical
conductors may be buried or otherwise encased and the pipes simply lead to and
from the apparatus boxes. A current of air. is forced down the intake pipe a
from blower A and after passing through the boxes travels up the return pipe b
to a nozzle or other opening d by which the discharge and consequently the
pressure in the pipes and boxes can be governed. The pressure in the pipes is
also exerted ou a water gauge e carrying a float f connected to an electric switch

page_text: which may consist of a bridge piece g which on rising or falling will break or
make circuit through mercury cups arranged in a circuit with electro magnets h
which hold or release the main switches ii depending upon whether the circuit
through the cups is maintained or not.
The main switches ii preferably have an armature or iron lever jj pivoted at
one end and on the same centre therewith but separate therefrom is a switch arm
or lever i which when raised will electrically connect two contacts and so
complete the main circuit. When the switch arm ii is raised so as to make
electrical connection with the two contacts, a catch or pawl k will engage with a
projection on the switch arm ii and so hold the said arm in position. On the
armature will be a projection or cam / which when the armature drops will push
on one side the catch or pawl k and cause it to disengage from the projection on
the switch arm i i, and the switch arm will then drop.
j
A spring m may be arranged to force the switch arm away from the contact,
the remainder of the drop being caused by gravity. A handle may be fixed
to the armature to raise it into position, and there may be a projection on the
armature which projects under the switch arm, so that when the armature is raised
into position the switch arm is also raised into position, so that there is little
likelihood of the switch arm being raised without raising the armature.
It will be seen that according to this invention the whole of the electrical
apparatus is contained in fresh air forced in from the surface, and if by any
accident or negligence any of the pipes, tubes, cases or boxes should be broken or
the covers removed so that there is danger of the electrical apparatus coming in
contact with the gases in the mine, the electrical circuit will immediately be
broken and the electrical current stopped owing to the air escaping at the break,
and consequently the air pressure falling at the point where the make and break
apparatus is actuated, fresh air at the same time being provided from the surface
at the point of fracture.
When desired the air may be forced through both pipes or what will probably
be preferable the two cables or one concentric cable containing both conductors may
pass through a single pipe from which branches may be taken where necessary,
each branch containing its two conductors and its automatic switch which in this
case would be located on each branch in the mine or at or near the point where the
branch is made.
In this case the fresh air would be forced through the pipe and a regulated
quantity would be discharged through each nozzle d while the switch may not
only cut off the current but also the air to each particular branch.should the pipe
or casing of same be broken or opened so as to avoid any shutting off the current
to other branches. When the air is discharged into the mine it of course assists
in ventilating same and it is thought that it will practically be preferable to allow
for a constant discharge through the nozzles although it will be evident that a
closed air circuit maintained at a constant pressure would answer the same
purpose.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. In electric systems the utilization of an air blast or pressure for auto-
matically operating the switches for the purposes set forth.
2. In electric systems the combination with an air discharge pipe, of a pressure
gauge and an electric circuit breaker operated thereby and adapted to release the
inain switches when the. air pressure falls substantially as and for the purposes
set forth.
3. In electric systems the combination of a switch arm, a catch adapted to
normally hold said switch in its closed position, and an armature normally held
in position by an electro magnet but adapted when released therefrom to release
the switch arm all substantially as described.

page_text: 4. The improvements in electric systems and apparatus arranged and combined
substantially as hereinbefore set forth.
Dated this 21st day of August 1894.
PHILIP M. JUSTICE,
55 & 56, Chancery Lane, London, W.C., Chartered Patent Agent,
For the Applicants.