Year: 1886

page_text: Date of Application, 2nd June, 1886
Complete Left, 2nd Mar., 1887.
Complete Accepted, 15th Apr.,
1887.
I JOSIAH VAVASSEUR of the London Ordnance Works Bear Lano Southwark in.
the County of Surrey Engineer do hereby declare the nature of this invention to be
as follows:-
This invention has for its object improvements in breech loading ordnance, and in
projectiles therefor.
At the present time in order to make a gas tight joint in rear of the powder chargo
it is usual to employ an "obturator" or stopper having a massive head entoring the
powder chamber and a stem which is received into a central cavity in the breech
block. Between the fore end of the breech screw or block and between it and the
rear surface of the head of the obturator an annular bag filled with asbestos and
tallow is placed. When the head is driven back on firing, the bag is compressed and
its periphery is forced so tightly against the walls of the powder chamber that a
perfect joint is obtained.
The object of the prosent invention is to avoid the loss of length in the powder
chamber (and consequent loss of length in the gun itself) which result from the
massive head of the obturator being inserted into it in front of the annular bag-and
at the same time to lessen the weight, and reduce the reactive effect after firing of
the head of the obturator upon its stem.
I reduce considerably the sectional dimensions of the annular bag and in place of
arranging it to abut upon the flat rear face of the obturator head as is the practice at
present, I place the bag in a groovo around the head of the obturator which for the
most part is within the circuit of the bag and projects into a corresponding recess in
the face of the breech block. As the dimensions of the bag are reduced I do not
allow the full pressure resulting from the explosion to fall upon it, but I support the
head of the obturator by a spring in rear of the head which being compressed at the
same time as the bag serves after a limited amount of compression as a solid abutment
for the head of the obturator and thus regulates the amount of compression of the
bag limiting it to that necessary to form a gas tight joint. Adjusting washers can
also be inserted between the elastic head and the abutment for this purpose.

page_text: The spring is lodged in the cavity provided in the face of the breech block to
receive the head; it consists of a double ring of steel, U form or troughed in
transverse section, with the open side of the trough directed inwards towards the stem
of the obturator, whilst the rounded angle is outwards and abuts upon the outer wall
of the cavity in the breech block.
Sometimes I make the head of the obturator in a still lighter form and so as to be
elastic around its periphery and to yield to the explosion whilst the central part is
supported by a solid abutment.
I form the circumferential part of this obturator so that after yielding to the
pressure of discharge to a certain extent it brings up against a solid abutment thus
regulating the amount of pressure upon the bag and thereby limiting it to that which
is necessary to form a gas tight joint as in the former case.
Or according to another plan I permit the central portion of the elastic head of the
obturator to yield rearwards to the explosion, the head being then of a convex form.
The compression of the centre of the head by the explosion expands the periphery,
and so as before the bag is forced into gas tight contact with the walls of the powder
chamber.
At present it is usual in ordnance to connect the larger diameter of the powder
chamber with the smaller diamoter of the bore by an intermediate inclined surface
leading casily from the chamber to the bore; this incline serves to conduct the
projectile into its place in the bore when it is inserted at the open breech. It is found
however that this inclined surface is quickly eroded-to avoid which I form an
abrupt shoulder at the end of the powder chamber making the bore to terminate
within the powder chamber in a shoulder or angle which is somewhat less than a right
angle. The diameter of the bore at the entrance is somewhat greater than the
diameter as measured in other parts to the bottom of the rifled grooves. The projectile
has a copper ring around it which fits this enlarged extremity of the bore and which
also has at its rear end a shoulder upon it of somewhat larger diameter.
The copper ring on the projectile is usually made of a diameter slightly larger
than the bottom of the grooves, but when the ring is very broad the amount of excess
or crush that can be given is very limited otherwise heavy pressures are liable to be
caused in the gun. On the other hand if the crush allowed is too little a very slight
enlargement of the gun which often occurs after firing a certain number of rounds
allows the powder gas to rush over the projectile between the ring and the bottom
of grooves thereby causing rapid erosion in the bore. I form the ring with the
shoulder at its rear end, made comparatively short, and with a very large amount of
crush, so that while it will be readily crushed over on firing without causing abnormal
pressure, it will always completely fill the bore even after considerable wear in the
latter, and stop the escape of gas around the projectile thus obviating the erosion due
to that cause.
This shoulder when the shot is in its place, abuts upon the extremity of the bore
whilst the end of the projectile itself extends into the powder chambor.
The end of the projectile is concave (as I have described in a former Provisional
Specification) with a view to prevent erosion in the bore.
T
T
1000
CARPMAEL & Co.,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in Breech Loading Ordnance and in Projectiles
therefor.
I, JOSIAH VAVASSEUR of the London Ordnance Works, Bear Lane, Southwark in
the County of Surrey, 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 :—
This invention has for its object improvements in and relating to breach loading
ordnance and projectiles.
At the present time in order to make a gas tight joint in rear of the powder charge
it is usual to employ an "obturator" or stopper having a massive head entering the
powder chamber and a stem which is received into a central cavity in the breech block.
Between the fore end of the breech screw or block and between it and the rear
surface of the lead of the obturator an annular bag filled with asbestos and tallow is
placed. When the head is driven back on firing the bag is compressed and its
periphery is forced so tightly against the walls of the powder chamber that a perfect
joint is obtained.
The object of the invention is to so modify the present construction as to avoid the
loss of length in the powder chamber (and consequent loss of length in the gun
itself) which result from the massive head of the obturator being inserted into it in
front of the annular bag and at the same time to lessen the weight and reduce the
reactive effect after firing of the head of the obturator upon its stem.
I reduce considerably the sectional dimensions of the annular bag and in place of
arranging it to abut upon the flat roar face of the obturator head as is the practice at
present, I place the bag in a groove around the head of the obturator which for the
most part is within the circuit of the bag and projects into a corresponding recess in
the face of the breech block. Or I make the obturator head without a groove and
insert the pad in a groove formed around the front end of the breech block. As the
dimensions of the bag are reduced I do not allow the full pressure resulting from the
explosion to fall upon it, but I support the head of the obturator by a spring in rear
of the head which being compressed at the same time as the bag serves after a limited
amount of compression as a solid abutment for the head of the obturator and thus
regulates the amount of compression of the bag limiting it to that necessary to form a
gas tight joint. Adjusting washers can also be inserted between the elastic head and
the abutment for this purpose.
The spring is lodged in the cavity provided in the face of the breech block to
receive the head, it consists of a double ring of steel Ụ form or troughed in transverse
section with the open side of the trough directed inwards towards the stem of the
obturator whilst the rounded angle is outwards and abuts upon the outer wall of the
cavity in the breech block.

page_text: Sometimes I make the head of the obturator in a still lighter form and so as to bo
clastic around its periphery and to yield to the explosion whilst the central part is
supported by a solid abutment and there is no movement to the rear of the stem of
the obturator.
I form the circumferential part of this obturator so that after yielding to the
pressure of discharge to a certain extent it brings up against a solid abutment thus
regulating the amount of pressure upon the bag and thereby limiting it to that which
is necessary to form a gas tight joint as in the former case.
In order that the breech block may be withdrawn by turning about a hinge at the
side of the gun I arrange the obturator to make the joint in a suitable conical seating
formed for it in rear of the powder chamber.
Another object of my invention is to prevent erosion of the interior of the gun.
At present it is usual in ordnance to connect the larger diameter of the powder
chamber with the smaller diameter of the bore by an intermediate inclined surface
leading easily from the chamber to the bore, this incline serves to conduct the
projectile into its place in the bore when it is inserted at the open breech. It is found
however that this inclined surface is quickly eroded to avoid which I form an abrupt
shoulder at the end of the powder chamber making the bore to terminate within the
powder chamber in a shoulder or angle which is somewhat less than a right angle.
The diameter of the bore at the ontrance is somewhat greater than the diameter as
measured in other parts to the bottom of the rifled grooves. The projectile has a
copper ring around it which fits this enlarged extremity of the bore and which also has
at its rear end a shoulder upon it of somewhat larger diameter.
The copper ring on the projectile is usually made of a diameter slightly larger than
the bottom of the grooves but when the ring is very broad the amount of excess or
crush that can be given is very limited otherwise heavy pressures are liable to be
caused in the gun. On the other hand if the crush allowed is too little a very slight
enlargement of the gun which often occurs after firing a certain number of rounds
allows the powder gas to rush over the projectile between the ring and the bottom of
grooves thereby causing rapid erosion in the bore. I form the ring with the shoulder
at its rear end made comparatively short and with a very large amount of crush, so
that while it will be readily crushed over on firing without causing abnormal pressure
it will always completely fill the bore even after considerable wear, in the latter, and
stop the escape of gas around the projectile thus obviating the erosion due to
that cause.
This shoulder when the shot is in its place abuts upon the extremity of the bore
whilst the end of the projectile itself extends into the powder chamber.
My invention is illustrated by the annexed drawings.
DESCRIDAIAN AN
Figure 1 is a longitudinal section of the breech end of a gun illustrating one of the
forms of obturator above described.
Figures 2 and 3 are sections of other forms.
Figure 4 is a longitudinal section of the breech end of a gun showing the obturator
so arranged as to admit of the breech being opened by the movement of the breech
block about a hinge joint.
Figure 5 shews the same parts as Figure 4 but with the breech block in the open
position.
Figure 6 shews the way in which I form the junction between the powder chamber
and bore of the gun and also the flanged ring on the projectile.
In Figure 1 A A are the walls of the gun and B is the breech block. The breech
block is locked in its place by a divided screw of two diameters as is well understood.
C is the obturator which has a concave face and recedes within the pad entering into
a cavity provided in the face of the breech block. D is a spring provided in this
cavity, after yielding to a certain extent it forms a dead stop and so limits the amount
of pressure coming upon the obturator pad E. This pad is much smaller in

page_text: dimensions than is usual. The stem of the obturator passes through the breech block
and is retained by a nut as is usual and the vent is through the stem.
In Figure 2 the head of the obturator is flexible and in yielding into the recess
provided on the face of the breech plug it compresses the obturator pad E. The
dotted line in front of the obturator shews the extent to which obturators as heretofore
nade would have projected into the bore.
In Figure 3 the head of the obturator is shown of another form; it is flexible and
when the charge is fired it yields until it rests against the face of the breech block.
In this case the breech block is recessed to receive the obturator pad.
In Figures 4 and 5 the powder chamber of the gun is shown to terminato in a
conical scating at I and against this seating the obturator pad E closes. The spaces
between the screw thread in the breech of the gun are also suitably cut away to allow
the breech block to clear when swung round. This construction as will be seen admits
of the breech block when unlocked being withdrawn by a circular movement around a
point at K.
In Figure 6 the junction of the powder chamber and bore of the gun is marked F.
The powder chamber terminates in front in a shoulder which is nearly a right angle
but preferably somewhat less-this formation lessens the erosion which otherwise
occurs about the end of the powder chamber and the entrance to the bore. G is the
flanged copper ring on the projectile. The flange rests against the shoulder of the
powder chainber and it is crushed down when the gun is fired, being narrow it may
be materially reduced in diameter without causing too much resistance, and it will
prevent the powder gasos passing oven when the bore has become considerably
enlarged by wear.
Having now particularly described and ascertained the nature of my said invention
and in what manner the same is to be performed I declare that what I claim is :-
1. Forming the face of the breech block with a cavity to receive the head of the
obturator.
2. Making the head of the obturator clastic or flexible so that by its change of
form it causes the pad to be compressed.
3. The conical seat at the rear end of the powder chamber and the pad of the
obturator making a joint against this conical seat in combination with the breech
block capable of being withdrawn by a circular movement as described.
4. The square or nearly square shoulder at the fore part of the powder chamber.
5. The flanged ring on the projectile abutting against the shoulder in the powder
chamber.
6. The several improvements as illustrated by the annexed drawings.
n