IMPROVEMENTS IN ORDNANCE
Year: 1882

page_text: LETTERS PATENT to Josiah Vavasseur of the London Ordnance Works
Bear Lane Southwark in the County of Surrey for an Invention of
"IMPROVEMENTS IN ORDNANCE
"
PROVISIONAL SPECIFICATION left by the said Josiah Vavasseur at the
Office of the Commissioners of Patents on the 22nd November 1882.
JOSIAH VAVASSEUR of the London Ordnance Works, Bear Lane, Southwark
in the County of Surrey "IMPROVEMENTS IN ORDNANCE"
This Invention has for its object improvements in ordnance and relates especially
to devices for obtaining greater strength longitudinally.
Where tubes forming a gun are fitted over each other any tendency for one
to slide on the other longitudinally from the effect of firing has been hitherto
counteracted either by screwing the parts together or by leaving comparatively
shallow projecting rings or collars on one piece to be shrunk into corresponding
recesses formed in the other piece both methods require great accuracy of
adjustment especially for the shrinking process.
My improved method consists in cutting a coarse screw groove on the exterior
of the inner piece or tube at the part where is desired to couple it to the outer
piece and to cut an exactly corresponding groove in the bore of the outer piece
so that when the two pieces are shrunk or fitted together there will remain a
spirally formed recess by preference square or rectangular in section into which
I pass a spirally formed bar of steel or other metal of corresponding section to fit
as closely as possible into the space thus left for it. The two tubes will thus be
ongitudinally coupled together by the spiral bar which must be sheared or
deformed before one can slide on the other to any extent likely to endanger the
tructure I prefer making the thread in such a direction with respect to the
ifling of the tube that any tendency to move the tube on its axis will tend to
crew the tube further into its jacket or the piece to which it is coupled.
In breech closing arrangements formed with screws of interrupted thread, instead

page_text: of making the screw thread uniform in diameter throughout its whole length I
form it of two or more steps that next the bore being the smallest and successively
increasing towards the breech the threads being at the same time kept out of line
with each other longitudinally. The effort of the exploded charge to blow out
the breech screw is thus transmitted both to the several layers of metal of different
diameters in which the screws engage and is also distributed around an entire
-circle or nearly so instead of only on a half circle as at present My proposed form
of screw allows of the breech being opened with much less longitudinal movement-
of the screw after unlocking than with a screw of uniform diameter. In some cases
instead of forming screw threads on the plug for closing the breech I make annular
rings similar to a thread in Section.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Josiah Vavasseur in the Great Seal Patent Office on the
21st May 1883.
JOSIAH VAVASSEUR of the London Ordnance Works Bear Lane Southwark
in the County of Surrey. "IMPROVEMENTS IN ORDNANCE"
This invention has for its object improvements in ordnance and relates especially
to devices for obtaining greater strength longitudinally.
Where tubes forming a gun are fitted over each other any tendency for one
to slide on the other longitudinally from the effect of firing has been hitherto
counteracted either by screwing the parts together or by leaving comparatively
shallow projecting rings or collars on one piece to be shrunk into corresponding
recesses formed in the other piece-both methods require great accuracy of
adjustment especially for the shrinking process.
My improved method consists in cutting a coarse screw groove on the exterior
of the inner piece or tube at the part where it is desired to couple it to the outer
piece-and to cut an exactly corresponding groove in the bore of the outer piece
so that when the two pieces are shrunk or fitted together there will remain a
spirally formed recess by preference square or rectangular in section into which
I pass a spirally formed bar of steel or other metal of corresponding section to fit
as closely as possible into the space thus left for it. The two tubes will thus be
longitudinally coupled together by the spiral bar which must be sheared or
deformed before one can slide on the other to any extent likely to endanger the
structure. I prefer making the thread in such a direction with respect to the
rifling of the tube that any tendency to move the tube on its axis will tend to
screw the tube further into its jacket or the piece to which it is coupled.
In breech closing arrangements formed with screws of interrupted thread instead
of making the screw thread uniform in diameter throughout its whole length-I
form it of two or more steps, that next the bore being the smallest and successively
increasing towards the breech, the threads being at the same time kept out of line
with each other longitudinally. The effort of the exploded charge to blow out
the breech screw is thus transmitted both to the several layers of metal of different
diameters in which the screws engage and is also distributed around an entire
circle or nearly so instead of only on a half circle as at present. My proposed form
of screw allows of the breech being opened with much less longitudinal movement
of the screw after unlocking than with a screw of uniform diameter. In some
cases instead of forming screw threads on the plug for closing the breech I make
annular rings similar to a thread in section.
In order that my said invention may be most fully understood and readily
carried into effect I will proceed to describe the Drawings hereunto annexed.
DESCRIPTION OF THE DRAWINGS
Figure 1 is a longitudinal section of two portions of a gun united in accordance
with my invention. A is the outer and B the inner part. Within A a spiral
groove is cut and a like groove is cut upon the exterior of B. The outer part is
then shrunk upon the inner in the usual way but with care that the grooves
shall coincide and form a spiral passage. A spirally formed bar of steel or other
suitable metal C, of a size just to be able to pass is then inserted by screwing it
into the passage.
Figure 2 is a section of the breech of a gun made in accordance with my
invention. In this Figure the breech screw or plug is in its place and the breech
closed as for firing.

page_text: Figure 3 is also a sectional view, here the breech screw or plug is represented
as drawn back and ready for opening the breech. The dotted lines represent the
position of the plug and other parts when the breech is partly open.
Figure 4 is a rear view of the gun with the breech closed.
In the gun represented the screw is in two steps. a¹ and a² are the two steps
in the gun, they are two successive enlargements of the bore, and in each there
are two groups of internal screw threads a*. a*. separated by intervals somewhat
wider than the groups and the groups in the step a¹ are opposite the intervals in
the group a
The breech plug has two corresponding steps upon it b₁ and 62 and on each are
two groups of external screw threads b*. *. and adapted to engage-with-the
threads within the breech of the gun.
In place of screw threads portions of annular rings may as already stated be
substituted. The number of steps may be increased if desired.
The breech plug is conveniently carried in a ring or collar c. through which
it can slide and in which it can also turn, the movement being however limited
by the stop c'. The ring or collar c is jointed at c. to the breech of the gun.
6 and bare handles upon the plug by which it can be turned and moved
backwards and forwards.
Having thus described the nature of my said Invention and the manner of
performing the same I would have it understood that I claim as my improvements
in ordnance.
First. The method of securing two parts A and B so as to restrain longitudinal
movement of the one on the other by the coinciding grooves enclosing a spiral
passage into which a correspondingly formed bar of metal C is made to enter
substantially as described.
Second. The arrangement of the breech action of a breech loading cannon
consisting in providing successive steps a¹ and a². within the gun and corre-
sponding steps b' and 6' upon the breech plug and having on such steps groups of
threads a. a*: and 6*. 6+. passing partly around and separated by intervals
between the groups substantially as described.
In witness whereof I the said Josiah Vavasseur have hereunto set my hand
and seal this nineteenth day of May in the year of our Lord One thousand
eight hundred and eighty three.