improvements in Breech Loading Ordnance.
Year: 1898

page_text: Date of Application, 21st Nov., 1898
Complete Specification Left. 19th Aug. 1899 Accepted 14th Oct
1899
improvements in Breech Loading Ordnance.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, do hereby
declare the nature of this invention (which has been communicated to me from
abroad by Frank Friday Fletcher, Lieutenant in the United States Navy, of
1441, Massachusetts Avenue, in the City of Washington, in the District of
Columbia, in the United States of America,) to be as follows:-
The invention relates to breech loading ordnance in which a breech block or
plug is locked in the breech chamber or plug box by a partial turn and may
readily be unlocked by a reverse partial turn to permit of its being withdrawn
longitudinally or swung outwardly to open the breech.
The object of the invention is to provide an organization affording an increased
area of engagement between the plug and its box thereby permitting a corre-
sponding reduction in the thickness or length and weight of the plug.
In the improved organization the exterior of the breech plug or screw plug
is of a spiral or snail-shaped contour; that is to say, its radius with reference
to the point or center from which the curve is constructed uniformly gradually
increases, or substantially so, from its shortest radius, which may be at or near
the bottom of the block, to its longest radius, which may coincide with its shortest
radius. This produces a shoulder the face of which lies in the line of the longest
and shortest radii. The interior of the box is similarly shaped with reference
to the same center. The surface of the plug or breech block may be formed with
screw threads extending from the angle of the shoulder farthest from the center,
substantially around its periphery, say, for instance, through five-sixths of the
periphery. The interior face of the box or breech chamber may be provided with
corresponding screw threads of like length starting from the angle of the
shoulder nearest the center. The relative dimensions of the plug and chamber
are such that when the shoulder of the plug is brought in line, or substantially.
so, with the shoulder of the box the plug may be caused to enter the box. When
so entered a partial turn of the plug, say from one-sixth of a complete revolution,
seats the threads of the plug in the threads of the box. During this partial
rotation the threads of the plug throughout their area enter the threads of the
box at a uniform, or substantially uniform, velocity. The angle at which the
threads engage depends, of course, upon the pitch or fall of the spiral curve. This
angle may be made of any acuteness so as to afford the desired screw action to
seat the plug solidly.
.
Instead of forming the plug (and correspondingly the box) with a single
shoulder at which the long and short radii of the spiral curve meet, two shoulders
may be formed on opposite sides of the plug with spirally curved faces between
them. In such case the longest radius of one curve and the shortest radius of
the other curve will terminate in the line of the face of each shoulder.
In the construction which has been described the spiral curve or curves is
not an arc of a circle. To this feature of construction is due the facts that an

page_text: engagement is possible of the plug and box throughout approximately the entire
area of their faces; that the threads on the spiral faces engage throughout their
length with a uniform velocity, and that a screw action is obtained which results in
the plug being solidly seated in the box. The breech block or screw plug may
be formed with straight surfaces parallel with its axis or it may be tapered through-
out or at its end. Preferably the surface of the breech block has a single thread
which extends spirally and helically from one end of the block's surface,
being necessarily broken only at the point where the longest and shortest radii
coincide.
The breech chamber or screw box is formed with a longitudinal channel
which receives the shouldered portion of the breech block when it is first
inserted.
The depth of the thread should, to give the best results, correspond with the
form of the spiral. Preferably the depth of the thread is equal to one-sixth of
the distance from the inner end to the outer end of the shoulder. So that when the
breech block is turned through an arc of sixty degrees, one-sixth of a revolution,
the highest point of the screw thread on the block will be made to engage the
thread of the breech chamber or screw box at the point which is farthest from the
center thereof, and similarly, portions of the thread having gradually decreasing
radii will engage corresponding parts of the thread in the screw box. The screw
plug may revolve about an axis which coincides with the axis of the bore of the
gun, or the screw plug may revolve about an axis out of line with the axis of
the bore, in which case the center point of pressure of the powder gases in the
bore may be made to coincide with the center point of resistance offered by the
screw-thread area of the breech block when it is locked in the breech chamber..
Instead of employing screw threads, suitably shaped collars may be employed.
Dated this 21st day of November 1898.
Improvements in Breech Loading Ordnance.
I, SYDNEY PITT, of Sutton, in the County of Surrey, Gentleman, do hereby
declare the nature of this invention (which has been communicated to me from
abroad by Frank Friday Fletcher, a Lieutenant in the United States Navy,
residing at No. 1441, Massachusetts Avenue, in the City of Washington, District
of Columbia, U.S.A.,) and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:
-
The invention relates to breech loading ordnance in which a breech block or
plug is locked in the breech chamber or plug box by a partial turn and may
readily be unlocked by a reverse partial turn to permit of its being withdrawn
longitudinally or swung outwardly to open the breech.
In the improved organization the exterior of the breech plug or screw plug
is of a spiral or snail-shaped contour; that is to say, its radius with reference
to the point or center from which the curve is constructed uniformly gradually
increases, or substantially so, from its shortest radius, which may be at or near
the bottom of the block, to its longest radius, which may coincide with its shortest
radius. This produces a shoulder the face of which lies in the line of the longest
and shortest radii. The interior of the box is similarly shaped with reference
to the same center. The surface of the plug or breech block may be formed with
screw threads extending from the angle of the shoulder farthest from the center,
substantially around its periphery, say, for instance, through five-sixths of the
periphery. The interior face of the box or breech chamber may be provided with

page_text: corresponding screw threads of like length starting from the angle of the
shoulder nearest the center. The relative dimensions of the plug and chamber
are such that when the shoulder of the plug is brought in line, or substantially
80, with the shoulder of the box the plug may be caused to enter the box. When
so entered a partial turn of the plug, say from one-sixtli of a complete revolution,
seats the threads of the plug in the threads of the box. During this partial
rotation the threads of the plug throughout their area enter the threads of the
box at a uniform, or substantially uniform, velocity. The angle at which the
threads engage depends, of course, upon the pitch or fall of the spiral curve. This
angle may be made of any acuteness so as to afford the desired screw action to
seat the plug solidly.
Instead of forming the plug. (and correspondingly, the box) with a single
shoulder at which the long and short radii of the spiral curve meet, two shoulders
may be formed on opposite sides of the plug with spirally curved faces between
them. In such case the longest radius of one curve and the shortest radius of
the other curve will terminate in a line of the face of each shoulder.
In the construction which has been described the spiral curve or curves is
not an arc of a circle. To this feature of construction is due the facts that an
engagement is possible of the plug and box throughout approximately the entire
area of their faces; that the threads on the spiral faces engage throughout their
length with a uniform velocity, and that a screw action is obtained with results in
the plug being solidly seated in the box. The breech block or screw plug may
be formed with straight surfaces parallel with its axis or it may be tapered through-
out or at its end. Preferably the surface of the breech block has a single thread
which extends spirally and helically from one, end of the block's surface,
being necessarily broken only at the point where the longest and shortest radii
coincide.
The breech chamber or screw box is formed with a longitudinal channel
which receives the shouldered portion of the breech block when it is first
inserted.
The depth of the thread should, to give the best results, correspond with the
form of the spiral. Preferably the depth of the thread is equal to one-sixtli of
the distance from the inner end to the outer end of the shoulder, so that when the
breech-block is turned through an arc of sixty degrees, one-sixth of a revolution,
the highest point of the screw thread on the block will be made to engage the
thread of the breech chamber or screw box at the point which is farthest from the
center thereof, and similarly, portions of the thread having gradually decreasing
radii will engage corresponding parts of the thread in the screw box. The screw
plug revolves about an axis out of line with the axis of the bore, so that the
center point of pressure of the powder gases in the bore is made to coincide with
the center point of resistance offered by the screw-threaded area of the breech
block when it is locked in the breech chamber. Instead of employing screw-
threads, suitably shaped collars may be employed.
In the accompanying drawings-
Figure 1 represents an end elevation of the breech of the gun and a transverse
section of the breech-block. In this figure the breech-block is shown as having
been inserted longitudinally in the breech chamber, but has not been locked
therein.
Fig. 2 is a view similar to Fig. 1, but with the breech-block turned and locked
in the breech.
Fig. 3 represents a longitudinal central section through the breech of the gun
on the line 3-3 of Fig. 1, the breech block being shown in side elevation.
Fig. 4 is a view similar to Fig. 1, of my improved construction in which the
center of resistance of the plug (which is the center of gravity of the plug
when in a horizontal position) will be in line with the center of strain exerted by
the powder charge, and in the construction shown, such center is coincident with
the axis of the bore of the gun.

page_text: The bore A of the gun, B, connects with an enlarged breech chamber or screw-
box, C. The breech-block or screw plug, D, may be formed with a straight
surface parallel with its axis or it may be tapered throughout, or at its end. Its
periphery, instead of being concentric with its axis, a, is of gradually increasing
radius. The shortest radius is between the axis, a, and the point, b, the longest
radius between the axis, a, and the point, e, while the radius from to c, c to d,
and d to e, gradually increases, thus giving to the breech block a cross section
which is spiral or snail-shaped, and not the arc of a circle, and produces a
shoulder, E, between the outer ends of the radii, a b, a e. The surface of the
breech-block is screw-threaded, a single thread preferably being used which
extends spirally or helically from end to end of the block's surface, being
necessarily broken only at the shoulder, E, but preferably also between the
points b and c.
The breech chamber or screw-box, C, is formed similarly to the breech-block
and is adapted to permit it to be inserted by a longitudinal or swinging movement
and to be withdrawn in the same manner. It is provided, preferably in its lower
wall, with a longitudinal channel, F, the form of which is shown in Figs. 2 and 3,
which is adapted to receive the shouldered portion of the breech-block when it is
first inserted, as indicated in Fig. 1, where, it will be observed, the breech opening
is of such size and shape as to clear the breech block when it is first inserted. That
is to say, the spirally curved walls of the breech chamber do not touch the walls
of the breech block when the latter is in the position shown in Fig. 1, with the
shouldered portion within the channel, F, but when the breech-block is turned to
the right, or in the direction of the hands of a watch, about its axis, a, the screw
threads on the block are made to engage and interlock with the screw-threads
in the chamber, and the parts will then occupy the. position indicated in Fig. 2,
where, as shown, the breech-block completely fills the chamber with the exception
of the channel, F, and the screw-threads are securely engaged. Thus is afforded
a large screw-threaded area for locking the parts together.
The depth of the thread should correspond with the form of the spiral. Prefer-
ably the depth of the thread is equal to one sixth of the distance from 6 to e
on the shoulder E so that when the breech-block is turned through an arc of sixty
degrees, or one sixth of a revolution, the highest point of the screw-thread on
the block, indicated at e will be made to engage the thread in the breech
chamber at the point, f, and similarly, portions of the thread having gradually
decreasing radii will engage corresponding parts of the thread in the breech
chamber. The depth of the threads may be varied but a fixed relation should
preferably always exist between the depth of the threads and the amount of
movement given to the block in order to produce the best results. For instance,
if the depth of the thread is equal to one-fourth the distance from 6 to c, the
construction should be such that the block may be turned one-fourth of a
complete revolution or through an arc of ninety degrees in order to completely
engage the threads. In like manner the blank or unscrew-threaded part of the
block (and likewise the channel F) should correspond with the arc through which
the block moves to lock it. When the block is moved through an arc of sixty
degrees, the blank space on the block and the width of the channel, F, subtends
an angle of sixty degrees. When the block is moved through an arc of ninety
degrees, the space and the channel should subtend an angle of ninety degrees, &c.
If it is desired to increase the depth of the thread without changing the arc
traversed by the breech-block, it may be accomplished by increasing the distance
from 6 to e and thus making the spiral more pronounced. In the same manner
the depth of the thread may be decreased by decreasing the distance from 6 to e,
and making the spiral less pronounced. While these relations are incident
to the construction shown in the drawings, they are not of the essence of the
invention.
The relations of the parts of the breech mechanism shown in the drawings
enable me to obtain sufficient clearance to insert and..withdraw the breech-block

page_text: freely and by this arrangement I am enabled to obtain a screw-threaded inter-
locking surface of about five-sixths or 833 per cent. of the entire periphery of
the block. Greater or less clearance may be obtained by increasing or diminishing
the width of the channel, F, and the blank space in the block opposite to it, with
a corresponding decrease or increase, respectively, of the screw-threaded inter-
locking surface.
There is or may be given sufficient clearance to insert and withdraw the block
without moving it fore and aft in a straight line longitudinally, but by simply
swinging it on a properly constructed hinged carrier. When the block or plug
is so handled, it and the box or chamber may have a taper form.
In the drawings I have indicated a construction wherein one continuous spiral
thread winds around the entire periphery of the breech block from end to end,
being interrupted only by the blank space or segment opposite the channel, F,
but the thread may be divided into sections and two or more shouldered
portions, E, may be employed, it being essential only that these parts should be
provided with threads of gradually increased radius. For instance, it would
be entirely feasible to provide the block with a shouldered portion at X and
form. the breech chamber with a corresponding channel but as a single shouldered
portion and a single channel fulfil all essential conditions, I prefer to employ this
construction. When I have spoken of a shouldered portion I have done so for
convenience in reference to the drawings, not because a shoulder is a necessary
feature of construction. Any suitable mechanism may be employed for support-
ing and operating the breech-block, and the breech-block may be equipped with
the usual firing and extracting mechanism, &c.
In Figs. 1 and 2 of the drawings a construction is shown in which the breech-
block revolves about an axis which coincides with the axis of the bore of the
gun, but by making the breech block revolve about an axis out of line with the
axis of the bore I gain an advantage, as by such construction the center point of
pressure of the powder gases in the bore may be made to coincide with the
center point of resistance offered by the screw-threaded area of the breech-block
when it is locked in the breech chamber.
Such a construction is clearly shown in Fig. 4, in which a is the axis about
which the plug turns in being brought into final position in the box; the center
of resistance or gravity of the plug, i.e., the point around which the plug would
balance if placed in a horizontal position and supported upon a needle point;
c the axis of the bore of the gun; A the circle indicating the bore of the gun
and of which is the center; and is a circle described around the point b
which is the strain center of the plug. As shown the plug has been inserted and
is ready to be turned. A partial revolution, say one-sixth, about the axis a
carries the center 6 through the arc b, c, when the centers be coincide.
In the two forms of my invention which have been illustrated the threaded spiral
or snail like curved faces of the plug and box are constructed from the center a
which is the axis of rotation of the plug.
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. A breech block having a threaded periphery which in cross section is a curve
of gradually decreasing radius, and adapted to turn about an axis out of line with
its center of resistance, in combination with a gun having a breech chamber
or screw box whose interior wall is correspondingly curved with a decreasing
radius.
2. A breech block having a threaded periphery which in cross section is a
curve of decreasing radius, and adapted to turn about an axis out of line with its
center of resistance, in combination with a gun having a breech chamber or
screw box, whose threaded interior wall is correspondingly curved with a decreas-
ing radius, the relation of the block and chamber being such that when the

page_text: block is inserted into the chamber a partial rotation of the block seats its threads
in the threads of the chamber and brings its centre of resistance into line with
the axis of the bore of the gun.
3. A breech block for ordnance, substantially as herein shown and described.
4. A breech block for ordnance having two sections of its periphery threaded,
each of which threaded sections being in cross-section a curve of gradually
increasing radius.
Dated this 21st day of July 1899.