Improvements in Firing Keys or Electrical Contact Makers.
Year: 1894

page_text: Date of Application, 6th Feb., 1894
Complete Specification Left, 5th Nov., 1894-Accepted, 8th Dec., 1894
PROVISIONAL SPECIFICATION.
Improvements in Firing Keys or Electrical Contact Makers.
I, HERBERT VIVIAN KEESON of 40 Loudoun Road, Saint John's Wood,
London, Gentleman, do hereby declare the nature of this invention to be as
follows:-
This invention relates to electrical contact makers for firing explosives.
The chief object of this invention is to obtain a firing key which will not close
the circuit by accident.
According to this invention the completion of the circuit depends not upon one
contact but upon a number of contacts. These contacts are complete simul-
taneously by compression by the fingers or hands.
According to this invention the firing key consists of a vulcanite tube. In the
middle of this tube is a metal plate which is prepared for contact on both sides.
Inside each end of the tube is a metal plunger or push which slides to and from
the middle contact plate. The circuit is not closed until the two metal plungers
are simultaneously touching the middle plate. For additional security these
plungers or pushes are sunk or recessed below and inside the ends of the tube.
Dated this Fifth day of February 1894.
COMPLETE SPECIFICATION.
Improvements in Firing Keys or Electrical Contact Makers.
I, HERBERT VIVIAN KEESON, of 40 Loudoun Road, Saint John's Wood,
London, Gentleman, 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 :-
This invention relates to electrical contact makers for firing explosives and for
other purposes.
The chief object of this invention is to obtain a firing key which will not close
the circuit by accident.
According to this invention the completion of the circuit depends not upon one
contact but upon a number of contacts. These contacts are completed simul-
taneously by compression by the fingers or hands.
According to this invention the firing key consists of a vulcanite tube. In the
middle of this tube is a metal plate which is prepared for contact on both sides.
Inside each end of the tube is a metal contact actuated by a plunger or push which
slides to and from the middle contact plate. The circuit is not closed until the two
contacts are simultaneously touching the middle plate. For additional security
these plungers or pushes are sunk or recessed below and inside the ends of the
tube.
Figure is a side elevation, Figure 2 an end view and Figure 3 a longitudinal
section of such an arrangement. Figure 4 is an end view with the cap and push o
removed.
c is a push
fixed to the
screw g and
a is a cylindrical block of vulcanite, b is a cap screwed to it.
working in the cap b and bearing upon the spiral spring d which is
block a by the screws e. f is a spring fixed to the block a by the
bearing upon the push working in the screw plug j. k is a metal contact plate
Price 8d1

page_text: screwed into the block a. I and m are wires connected to the spring d and plate k
respectively.
In order to complete the circuit through the wires and m it is necessary not
only to press in the push e until the projection d' on the spring d comes into contact
with the springf but also to press the push to bring the spring finto contact
with the plate k.
It will thus be seen that the circuit can only be accidentally closed by two
simultaneous blows in different directions which is very unlikely.
In place of having the push c at the end of the tube it may be sunk or recessed
below and inside the end in a similar way to h.
It is not essential to have two breaks in the circuit as the pushes might be made
to meet each other.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. A firing key or contact maker in which in order to close the circuit it is
necessary to operate two distinct pushes one or both of which is or are sunk or
recessed below and inside the end of the body.
2. The combination of a block or body with two contact making pushes acting
in directions at right angles or approximately at right angles to each other.
3. Firing keys or contact makers substantially as described and shown in the
drawings.
Dated this 1st day of November 1894.
HERBERT V. KEESON.