Improvements in or relating to Means for Delaying the Movement of the Projectile in Pneumatic Guns.
Year: 1889

page_text: Date of Application, 30th Oct., 1889-Accepted, 7th Dec., 1889
DI BOITICATION.
Improvements in or relating to Means for Delaying the Movement
of the Projectile in Pneumatic Guns.
A communication from HENRY EICHBAUM, of Hotel Burgundy, No. 8, rue Duphot,
Paris, in the Republic of France, Engineer.
I, ALFRED JULIUS BOULT of 323 High Holborn in the County of Middlesex,
M.I.M.E., 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 :-
The object of this invention is to prevent the projectile in a pneumatic gun from
being blown out by the first impulse of air that enters the barrel before the pressure
of the air has accumulated in sufficient force to act efficiently to propel the projectile,
and thus to secure a greater range without increasing the air pressure to a dangerous
degree.
As the projectiles of pneumatic guns are generally intended to be charged with
high explosives it is important in thus delaying the start of the projectile to so arrange
the means by which it is accomplished, that there shall be as little shock as possible
both in the start of the projectile from a state of rest and in its release from the force
that resists its movement.
The manner in which such delay and gradual start of the projectile is provided for
in this invention is shown in the drawings accompanying this specification in which
Fig. 1 represents a longitudinal section of the breech end of a pneumatic gun with
the breech closed and a projectile in external view ready to be discharged. Fig. 2
represents a longitudinal section on a larger scale of those parts of the barrel and
projectile in which the device is located. Fig. 3 shows a modification of part of
figure 2. The same letters refer to the same parts in all the figures.
A is the gun barrel or tube, A¹ being an opening through which air is admitted to
impel the projectile, and A² the breech block. B is the projectile, B¹ being the
chamber containing the explosive and B2 a gas check to prevent the impelling air
passing by the projectile in the barrel. Behind the gas check the shell of the
projectile is extended to allow of a wide dovetailed recess B³ being formed in its
circumference and this recess is filled with a ring of soft metal B such as
pewter, type metal, lead or any other suitable material, of somewhat larger diameter
than the rest of the projectile. A uniform diameter of this ring slightly larger
than the bore of the gun as shown in figure 3 may in some cases be sufficient to
delay the projectile to the desired extent without shock either at the start or
release but it is shown in Figs. 1 and 2 of such external shape that while at each
edge of the recess B³ it is the same diameter as the shell of the projectile it is
swelled in the middle to a larger diameter from which it tapers to either edge.
To accommodate this increased diameter of the projectile at this point, the barrel
at the breech is formed with a chamber A¹ of a diameter sufficiently large to
allow the.insertion of the projectile as shown in the drawings.
It is evident that as thus made the projectile cannot be discharged from the gun i
without the removal of all that part of the soft metal ring which projects beyond
the diameter of the barrel along which it has to travel to reach the muzzle. The
ring therefore offers a definite resistance to the movement of the projectile which
will allow the air pressure to accumulate to any desired amount dependent chiefly
upon the diameter and shape of the ring, the quality of the metal and the shape
and condition of the edge which strips it. To remove the projecting metal
of this ring so that the projectile may be discharged I place in a suitable position in
i

page_text: the gun barrel a cutting or stripping ring preferably of steel and of the same internal
diameter as the bore of the gun or slightly smaller which acts as a cutter or scraper
to strip off the soft metal as the pressure of the air forces the projectile for-
ward. This ring is shown at A Figs. 1 and 2. It may be made in-sections so as
to be placed from the inside in the recess in which it is shown, or it may be made in
one piece and the barrel so constructed as to allow of its insortion or removal. In
either case it is desirable that it should be hardened and tempered and its scraping or
cutting edge a³ kept in uniform condition as also the rings B of the projectiles so that
the amount of resistance should be the same with all projectiles.
In the drawing the steel ring is shown as just on the point of cutting the soft metal,
but if desired a short run may be allowed the projectile before the steel engages the
soft metal.
As shown in the drawings in figures 1 and 2 it is evident that the projectile would
move slightly at the first impulse of the air, and that as it advanced the increase of
the amount of soft metal to be removed would oppose more and more resistance to the
movement of the projectile. This would be met by the accumulation of the air
pressure which would at last overcome the resistance offered at the greatest diameter
of the soft metal ring. To provide against a shock by the sudden cessation of the
resistance the soft metal ring is tapered off at the rear edge as already described
and when this has passed the steel ring the projectile is free to traverse the gun
tube.
It will be perceived that considerable variations may be made in the details of
this invention without departing from the spirit of it; for example the shape, size,
position, or general arrangement of the ring and the place or manner of connecting
it to the projectile or a number of rings interchangeable or otherwise in a number
of segments might be used and similarly with the ring A3 for which many equivalents
might be devised. The placing of the solt metal in the gun and the stripping edge
upon the projectile would for many reasons be so undesirable that it is unnecessary to
dwell upon the numerous modifications which could the devised upon those lines.
The term "soft metal" is applied to the ring B in this specification but it
will be understood that other materials such for example as a suitable cement
might be used in place of metal and the term "soft metal" is intended to embrace
such other materials.
Merely to compare the purpose of the soft metal sabot of the ordinary shell with
the purpose of the soft metal ring of the present invention will suffice to establish
their entire dissimilarity both of purpose and .of operation The ordinary sabot is
designed to expand into the rifling grooves of the gun with which it then intercalates
acting as the male element of the rifling, but is not intended to have any retarding
effect upon the projectile. The soft metal ring of the present invention is, so far as
any extension beyond the diameter of the projectile is concerned, entirely removed
before it enters the gun tube proper, it is not intended to enter at all into the
rifling grooves: (if any) of the gun, and its special purpose is to retard the start of
the projectile until the predetermined pressure has been attained.
"Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, as communicated to me
by my foreign correspondent I declare that what I claim is
1. Retarding or delaying the movement of the projectile in a pneumatic.gun
barrel or tube by the removal of a portion of soft metal substantially as
described.
2. In .,a. device for retarding or delaying the movement of the projectile in a
pneumatic gun barrel or tube the combination with a soft metal obstruction upon
the projectile of a cutting .or stripping edge upon the gun substantially as
described.
3. In a device for retarding or delaying the movement of the projectile in a

page_text: pneumatic gun barrel or tube the combination with a soft metal ring such as B*
upon the projectile of a cutting or stripping ring such as A³ upon the gun sub-
stantially as and for the purpose described and illustrated in the accompanying
drawings.
4. The complete projectile retarding or delaying device substantially as described
and illustrated in the accompanying drawings.
Dated this 30th day of October 1889.
W. P. THOMPSON & BOULT,
Agents for the Applicant.