Improvements in Firing Keys.
Year: 1894

page_text: Improvements in Firing Keys.
HENRY CAPEL LOFFT HOLDEN Major, Royal Artillery Royal Arsenal
Woolwich do hereby declare the nature of this invention to be as follows:-
My invention relates to improvements in firing keys, such as are used for firing
the electric tubes of ordnance the electric fuzes of torpedoes, and of submarine
mines, as well as the electric fuzes used in blasting operations.
For the purpose of my invention, I construct a firing key, which may be either
of double or single pole form, in such a manner that in addition to its being used for
firing the tube or fuze it can also be employed to ascertain the ohmic resistance of the
circuit including the fuze before firing as also the current passing in the circuit
either when firing a tube or fuze in good order or when attempting to fire a tube
or fuze that is defective; these tests being made with the full battery or other
source of electric current. Furthermore the same arrangement or a part of it can
be employed for ascertaining the difference of potential at the terminals of the
firing battery or other source of electric current and thus ascertaining that the
same is in good order and fit for service.
To enable the above operations to be carried out, I construct my key with two
movements, the first with a view to testing the circuit without firing, and the
second with a view to testing and firing simultaneously or not as may be desired;
the first of the above mentioned movements may be a rotary one whilst the
second is a linear one or vice versa, or the first movement may be in one direction,
whilst the second is in the opposite direction, the object in either case being to
make the operations, firstly, for testing without firing and secondly for firing
definite and distinct from each other.
During the first portion i.e. that of testing, the movement of the key puts in
circuit the pressure coil of the indicating instrument, which shows the difference of
potential at the terminals of the battery if required; subsequently it also puts in
circuit the current coil of the indicator, this being included in the line circuit
together with a known extra resistance sufficient to prevent the tube or fuze firing,
this operation gives the total resistance in circuit, including the tube or fuze, but
without firing the same; from this the resistance of the line and tube or fuze
alone can be obtained by deducting the known value of the fixed extra resistance
above mentioned. The indicator is so acted upon by the combined action of the
pressure and current coil as to show on the dial the resistance in circuit;-at the
second movement the pressure and current coils are both in circuit but the extra
known resistance in the line is cut out, and consequently the tube or fuze fired, the
indicator showing at the same time the resistance of the circuit.
Dated this Seventeenth (17th) day of September 1894.

page_text: Improvements in Firing Keys.
HENRY CAPEL LOFFT HOLDEN Major Royal Artillery Royal Arsenal
Woolwich Kent 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 invertion relates to firing keys such as are used for firing the electric tubes of
ordnance, the electric fuzes of torpedoes or of submarine inines; and for the
purposes of my invention, I construct a firing key, which may be either of double
or single pole type, in such a manner that in addition to its being used for firing
the tube or fuze it can also be employed to ascertain the ohmic resistance of the
circuit including the fuze before firing as also the current passing in the circuit
or the resistance of the circuit at the moment of firing or any one or more of
these things with the full power of the battery or other source of electricity
employed. The key can also be used to ascertain the condition of the battery,
whether in good order or not.
In order that my invention may be more fully understood I shall now proceed
more particularly to describe the same and for that purpose shall refer to the
several figures on the annexed sheet of drawings, the saine letters of reference
indicating corresponding parts in both figures.
Fig. 1. represents in vertical section a firing key arranged according to my
invention, ZZZ is the case, made of metal or other suitable material, containing
the mechanism: A is the knob or bandle which is rigidly attached to the plunger. B,
this plunger being a working fit in the sleeve C, the sleeve C itself being attached
to the aforesaid case Z Z Z by a flange D. Just below the flange D in the
sleeve C there is a slot F a portion of which slot is cut circumferentially and a
portion longitudinally. In this slot F works a pin E which pin is rigidly fixed. in
the plunger B; thus the pin and slot control the movement of the plunger in such
a manner that it cannot be moved longitudinally until it has been turned to the
full extent allowed by the circumferential slot.
In turning the plunger B the pin E bears against one end of the spiral spring G,
the other end of this spring being attached to the collar H, which is fixed to the
sleeve C by the nut I and is adjustable so as to allow of the tension of the spring
being varied as required. The object of this spring is to restore the plunger to its
original position, whether its movement has merely been a turning one, or whether,
as will be hereinafter described, it has been a longitudinal movement as well.
The plunger B carries at its lower end a disc M of insulating material such as
ivory or ebonite, the object of which is to electrically insulate the plunger from
the battery or other source of electrical energy, connected to the springs N and O;
with these springs it is in mechanical contact when the plunger B is pushed in.
after being turned as far as the movement of the pin E in the slot allows. it
to go.
A portion of the plunger B is slotted at J as shown, a feather ou the circular
portion of the switch arm.Q R engaging in. this. slot J and therefore causing the
switch arm to turn with the plunger B, when the latter is turned, though not
having any tendency to move longitudinally owing to the feather being shorter
than the slot or featherway in which it works.
The circular portion of the lever R. Q. is kept in position by the cap K and the
bracket L between which it works; the bracket L may be conveniently attached
to the outer case Z Z Z.
The contact piece R on the switch arm R Q is insulated from the arm itself and
travels over the three sets of contacts S, S¹, S, S,¹, S, S, as the arm moves round

page_text: thereby completing the various circuits in turn. This portion of the apparatus is
seen in detail in Fig. 2.
The indicating portion of the instrument is comprised in the two bobbins U. V.
suitably wound to suit the particular conditions for which the apparatus may be
required.
The first bobbin U, however, is wound with insulated wire to a resistance
which is high compared to the resistance of the insulated wire on the second
bobbin V. The bobbin U being intended to act as a pressure meter whereas the
bobbin V is intended to act as a quantity meter.
The mechanism of these two meters, indicating the pressure and the quantity of
current flowing may be similar to any of the well known forms of pressure and
quantity meters, known generally as Volt and Amèpre meters; in this case,
however the mechanisins are connected to the same spindle carrying the pointer T,
and are actuated by the current so as to oppose each other's movement.
pointer T moves over the graduated scale X, the scale being visible through the
glazed portion W of the case Z Z Z.
The
The electrical connections are so arranged that when the plunger B is in the
position of rest, and the line wires proceeding to the fuze or tube are connected
both to the tube or fuze and also to the terminals of the firing key, no current will
pass. On turning the plunger B so that the the conducting portion of the switch
arm R makes contact between the contacts S, S₂-the current from the battery
passes through the wire on the bobbin U actuating the pointer T through the
mechanism and thereby showing from the position of the pointer T on the scale X,
the electromotive force or pressure at the terminals of the battery. On still
further turning the plunger B so that the portion R makes contact between S, S,,
the current is now allowed to pass through the wire on the bobbin U thence through
the line wires and tube back to the battery, thus giving an indication by means
of the pointer T of the resistance of the line wires and tube or fuze as compared
with the resistance of the coil U alone, in the third position the portion R makes
contact between the contacts S. S¹ and the current from the battery again passes
through the pressure coil U, in this case there may be a resistance in series or not
with this coil as the conditions may require. Whilst the switch arm is in this
position if the plunger B be pushed in so as to press the two springs N. O.
together, these being connected to the line wire, and one pole of the battery
respectively through the thick wire of the coil V-the other pole of the battery
being connected to the other line wire and the fuze or tube being at the same time
connected to the other two ends of the line wires, the full firing current will pass
and the tube or fuze be fired. The combined action of the two coils U and V on
the pointer T will cause the latter to show on the scale X the resistance of the
circuit at the moment of firing.
Obviously, if preferred, one or more of the sets of contacts S S¹, S, S₁₁, S, S,'
may be omitted the indications obtained from such contacts being consequently not
shown on the scale.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, declare that what I
claim is;
A firing key for firing the electric tubes or fuzes used with ordnance or
torpedoes, which in addition to its being used for firing the tube or fuze can be
also employed to ascertain the condition of the battery or other source of
electricity, the resistance of the circuit before firing and also at the moment of
firing, substantially as and for the purpose herein before described.
Dated this Seventeenth day of June 1895.
H. C. L. HOLDEN,
Major, R.A.