Improvements in Percussion Fuses for Explosive Projectiles.
Year: 1889

page_text: Date of Application, 22nd Nov., 1889
Complete Specification Left, 22nd Sept., 1890-Accepted, 15th Nov., 1890
PROVISIONAL SPECIFICATION.
Improvements in Percussion Fuses for Explosive Projectiles.
I, ABRAHAM MARTIN, of 177, Aston Lane, Birmingham, in the County of Warwick,
Engineer, do hereby declare the nature of this invention to be as follows :-
My invention relates to improvements in percussion fuses such as that forming the
subject of a previous application for Letters Patent dated the 1st day of January 1889
No. 39.
The said fuse is of that kind in which the point of the striking pin (by which the
detonation of the priming is brought about) is normally held retracted within a
weighted plunger so as to be incapable of acting on the priming but is caused by
virtue of the inertia of the weighted plunger (at the moment the gun is fired) to
assume such a position relatively to the plunger that on the projectile meeting an
obstacle the momentum of the weighted plunger will cause the striker to explode the
priming.
The plunger is encased in an inner sheath closed at the front end and an outer
sheath closed at the rear end the edges of the open ends of said sheaths being
respectively burred inwards to retain them in position, the sheaths fitting tightly.
The front end of the inner sheath has a central orifice just large enough to receive
the extreme point of the striking pin, the edges of the orifice being slit radially to
enable the pin to be easily forced through at the proper moment. The rear end of the
outer sheath is of approximately dome form, its convexity being normally outwards;
the rear end of the striking pin abutting against the internal surface of the domed
end of the sheath. The pin which passes freely through the bore of the plunger is
thus securely held between the front and rear ends, no loose play of the pin being
permitted and its point being retracted so as not to project beyond the front end of
the plunger.
Instead, however, of enclosing the butt end of the pin I may, by preference, rivet
it to the centre of the domed end so as to afford a two-fold security against
premature projection of the point of the pin beyond the front end of the plunger.
The rear end of the plunger is of concave form so that there is a hollow space of
lenticular form between it and the domed rear end of the sheath.
The fuse case (which is screwed into the base of the shell in the ordinary way and
in which the plunger is normally held without any play longitudinally therein) has an
internally projecting convex boss at the rear end opposed to and in contact with, the
dome-shaped end of the plunger.
When the gun is discharged, the inertia of the plunger causes it to remain
stationary when the projectile begins to move, so that the violent impact of the
convex boss of the fuse case against the hollow dome-shaped end of the plunger-
sheath causes the latter to be forced inwards until its curvature is reversed, thereby
forcing the striking pin forwards until its point projects in front of the plunger in
position to strike the priming. In this new form, the end of the plunger-sheath
presents a convex surface to the butt end of the pin and, owing to its form, it has
sufficient rigidity to enable the momentum of the plunger to carry the pin forcibly
forwards and cause it to strike with unfailing effect on the priming when the projectile
is suddenly arrested by striking an obstacle.
Dated this 22nd day of November 1889.

page_text: COMPLETE SPECIFICATION.
Improvements in Percussion Fuses for Explosive Projectiles.
I, ABRAHAM MARTIN of 177, Aston Lane, Birmingham, in the County of Warwick,
Engineer, 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 improved percussion fuse is of that kind wherein a plunger is by its inertia
first caused to bring the operative parts of the fuse into position for action and then
to determine the detonation of the priming, that is to say the point of the firing pin
is normally held retracted within a plunger so as to be incapable of acting on the
priming but is caused by virtue of the inertia of the plunger (at the moment the gun
is fired) to assume such a position relatively to the plunger that on the projectile
meeting an obstacle the momentum of the plunger will cause the firing pin or striker
to explode the priming.
Heretofore, in such fuses, as usually made, the connection of the plunger with the
firing pin has generally been more or less dependent on friction, both for retaining
the parts in their normal safe position and also for transmitting the force necessary
for effecting the explosion of the priming.
Such friction is liable to vary and become uncertain, and the object of my inven-
tion is to render the connection between the plunger and striker quite independent
of friction and more positive, in order that the parts shall be retained in the normal
inoperative position with absolute safety from premature explosion and that the
detonation of the priming shall be unfailingly brought about at the proper moment.
Reference is to be had to the accompanying drawings, forming part of this
Specification, wherein
Figure 1 is a longitudinal section of the fuse fixed in the base of the projectile and
shewing the normal form and position of the plunger.
Figure 2 is a similar view shewing the form and relative position assumed by the
plunger on the firing of the gun.
Figure 3 is a front view of the plunger only, the firing pin being in the safe
position.
The same letters of reference indicate like parts in all the figures.
A is the fuse case screwed into the body of the projectile in the ordinary way.
B is the plunger, being a cylinder (of copper or other metal, preferably Tungsten in
the form of compressed powder) having an axial orifice for the reception of the pin C.
The plunger is tightly encased in a sheath formed of a solid-drawn brass capsule b
whose rear end is normally convex or dome-shaped. It is preferred, especially
when the plunger is made of compressed Tungsten, to first enclose the plunger in an
inner capsule or sheath 62 closed at the front end and having its edges burred
inwards over the rear end of the plunger by pressure in a die. Over this inner
sheath the outer one b fits tightly the edges of the latter being similarly burred over
the front end of the former, as shewn.
The rear end of the plunger B enclosed by the dome-shaped end 6' of the sheath-b
is concave, as shewn, the curvature being opposite and about corresponding to that
of the end 6' of the sheath.
The striking pin C is contained in the axial orifice of the plunger and is confined
between the closed ends of the inner and outer sheaths its rear end either simply
abutting against the dome-shaped end 6' or preferably being rivetted into a central
orifice therein, as shewn so as to be dependent on the form of the domed end for
its position with regard to the plunger. Normally, the point of the pin is held
retracted within the front end of the plunger, this position of safety being ensured
both by the rivetted connection to the domed end 6 and also by the extreme point
of the pin being held in a central orifice in the front end of the inner sheath, the
edges of said orifice being radially slit. to enable the conical point of the pin to be
easily forced through as hereafter described. Such means of keeping the pin retracted

page_text: afford a two-fold security against the premature projection of the point of the pin
beyond the front end of the plunger, but either of them alone is efficient for the
purpose. The thickness of the metal of which I prefer to make the sheath is about
No. 27 Birmingham W.G. but I do not limit myself in this respect.
The fuse case A (which is screwed into the base of the shell in the ordinary way
and in which the plunger is normally held without any longitudinal play therein) has
an internally-projecting convex boss a at the rear end opposed to and in contact with
the dome-shaped end 6 of the plunger sheath, the convexity of this boss about.
corresponding to the concavity in the end of the body of the plunger.
The parts being in the normal position shewn in Figure 1 the point of the striking
pin is retracted so that in handling the fuse or the projectile the striker cannot be
brought into contact with the priming g which is held in place in the fuse case by
the ordinary means and communicates with the explosive charge by orifice h.
When, however, the gun is discharged the impact (due to the inertia of the
plunger) of the boss a against the hollow domed end 6¹ of the plunger sheath causes
the curvature of the latter to be reversed, as in Figure 2, whereby the pin C is forced
forwards until its point projects in advance of the plunger in position to strike the
priming g, such being the position of the pin during the flight of the projectile.
When the latter is suddenly arrested by striking an obstacle, the momentum of the
plunger carries the pin C forwards and causes it to strike with unfailing effect on the
priming, the full force due to the momentum being effective in consequence of
the rigidity of the end 6 due to its inwardly-arched form.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is;
1. A percussion fuse, whereof the striking pin is normally held retracted within a
plunger encased in a metal sheath having a hollow dome-shaped rear end but is
caused to project from the front end of the plunger by the inversion of the curva-
ture of the dome-shaped end of the sheath consequent on the impact due to the
inertia of the plunger, as specified.
2. In a percussion fuse, the combination, with a plunger having a concave rear end
and encased in a sheath having a hollow domed end, of a striking pin passing through.
the plunger and rivetted to said domed end and of a convex boss at the rear end of
the fuse case for producing the described alteration of shape of the domed end of the
sheath, as and for the purpose specified.
3. In a percussion fuse, the combination, with a tubular plunger having a concave
rear end, of a striking pin loose within it but confined between an apertured and
slitted front end and a hollow domed rear end of a sheath enclosing the plunger, as.
described, and of a convex boss on the fuse case opposed to the domed end of the
sheath for producing the described alteration of shape thereof, substantially in the.
manner and for the purpose specified.
Dated this 22nd day of September 1890.
MADTIN