IMPROVEMENTS IN APPARATUS TO BE USED WHEN FIRING FUSES BY ELECTRICITY
Year: 1873

page_text: PROVISIONAL SPECIFICATION left by Charles Ambrose M.Evoy at the
Office of the Commissioners of Patents, with his Petition, on the
2nd May 1878.
I, CHARLES AMBROSE M°Evoy, of the London Ordnance Works, Bear
Lane, Southwark, in the County of Surrey, do hereby declare the nature
of the said Invention for "IMPROVEMENTS IN APPARATUS TO BE USED WHEN
FIRING FUSES BY ELECTRICITY," to be as follows :—
The object of this Invention is mainly to construct apparatus for
indicating the ignition of electric fuses, in such a manner that the
insulated wire leading to a fuse shall when the fuse has been fired, be at
once disconnected from the battery, at the same time that the ignition
of the fuse is also indicated. By this means if a number of such fuses
are coupled up to the same battery, and one of them is ignited, the wire
which previously led from it is at once cut off automatically from the
battery, so that a current cannot pass out from the battery through the
broken end of the wire, and the full strength of the battery will be
maintained for igniting any of the other fuses which may have to be
fired. To effect this I connect the wire from the battery to a spring
.contact maker, which spring presses up to a metal surface from which a

page_text: wire is led to one end of the coils of an electro-magnet, and from the
opposite end of the coil, an insulated wire is led away to the electric
fuse.
'
Above the spring contact maker is a drum within which is a coiled
spring to cause the drum to rotate whenever it is set free; so long as no :
current passes from the battery the drum is retained from revolving by
one end of a lever being held down by a spring into a notch in its
periphery; the other arm of the lever carries the armature of the electro-
magnet. If a current is passed from the battery to ignite the fuse, it
first passes through the coils of the magnet, and by drawing down its
armature liberates the drum which is then revolved by the spring within
it until a projection on its exterior comes against the spring contact
maker before mentioned, and depresses it, so cutting off from the battery
the insulated wire which led to the electric fuse. When the drum has
turned into this position the word "fired," which is marked upon the
drum, is brought opposite an orifice in the outer casing of the apparatus ;
the word "set" is also marked upon the drum, and is opposite to this
orifice at the time when the drum is retained from revolving by the lever
catch before-mentioned, and when the battery is consequently coupled
up with the wire leading to the electric fuse. Any suitable means may
be used for controlling the speed at which the drum revolves when set
free, so that the current may pass from the battery to the fuse for a
sufficient length of time to insure its proper ignition, as for example by
regulating the strength of the spring, or by increasing or diminishing
the size of the drum, or teeth on the periphery of the drum may gear
with a small pinion from which motion is given to a "fly."
In place also of a revolving drum being used, a falling screen with the
words "set" and "fired" marked upon it may be used as the indicator,
and may similarly be caused to drop whenever a current passes from the
battery, and to cut off the battery from the wire leading to the fuse. In
this arrangement also, the duration of the current can be controlled as
before described.
Apparatus such as above described is especially applicable when
several electric fuses for igniting blasting charges are all coupled up
to one battery, or when one battery is used for the purpose of firing
any one of a number of submerged torpedoes, and is equally applicable
whether the fuses of the torpedoes are so constructed that a blow

page_text: transmitted to them causes them to complete the circuit, and so cause
ignition, or whether the completion of the circuit is to be effected at will
by coupling up a battery to the insulated wire leading from the fuse.
When the fuses are to be fired at will by coupling them up to a
battery I prefer to use for this purpose a contact maker of the following.
construction:-The contact maker is composed of a small cylinder of
ebonite, into one end of which is screwed a plug of the same material,
through the centre of which is carried a coated wire, and the wire is set
in electrical contact with a metal plate carried on the inside face of the
plug. Into the other end of the cylinder is also screwed a plug; this
plug is hollow and has an internal flange around its inner end; through
the hollow plug passes a plunger, and between them is a coiled spring
which rests at one end on the flange at the inner end of the hollow plug,
and at the other end against a shoulder on the plunger so that the spring
forces the plunger outwards, but the plunger is prevented from being
entirely forced out from the plug by a collar screwed on to its inner end.
A covered wire is passed through the plunger, and its end is bent over
against the collar. If the plunger is pressed inwards, the ends of the
two wires which are coupled to the two ends of the contact maker are
brought into electrical contact with one another, but so long as the
plunger is pressed outwards by the coiled spring before mentioned no
contact takes place. If one or other of the plugs be partly unscrewed
from the cylinder the contact maker will be set out of action, and no
contact can be made by any accidental pressing inwards of the plunger.
The apparatus above described is applicable generally as a contact
maker.