IMPROVEMENTS IN REVOLVING CANNONS
Year: 1878

page_text: LETTERS PATENT to William Morgan-Brown, of the Firm of Brandon and
Morgan-Brown, Engineers and Patent Agents, of 38, Southampton Buildings,
London, and 1, Rue Laffitte, Paris, for the Invention of "IMPROVEMENTS IN
REVOLVING CANNONS." A communication from abroad by Benjamin Berkley
Hotchkiss, of 1, Rue Laffitte, Paris.
Sealed the 4th October 1878, and dated the 30th July 1878.
COMPLETE SPECIFICATION filed by the said William Morgan-Brown at the
Office of the Commissioners of Patents on the 30th July 1878.
WILLIAM MORGAN-BROWN, of the Firm of Brandon and Morgan-Brown, Engineers
and Patent Agents, of 38, Southampton Buildings, London, and 1, Rue Laffitte,
Paris. "IMPROVEMENTS IN REVOLVING CANNONS." A communication from
abroad by Benjamin Berkley Hotchkiss, of 1, Rue Laffitte, Paris..
This Invention consists in several important improvements, on thie Hotchkiss
revolving cannon and other machine guns, but is particularly adapted to' thic
former.
The following is a description of these improvements, the accompanying three
Sheets of Drawings, with 28 Figures forming a part thereof, and of which,―
Figure 1'is a plan of revolving cannon; Figure 2 is a side elevation of the same';
Figure 3 is a front elevation; Figure 4 is a section through A, A, Figure: 2;
Figure 5 is a rear elevation:
Figure 6 is a front view on a larger scale of the breech of a revolving cannon
containing the mechanism; Figure 7 is a section through B, B, in Figure 9.
Figure 8 is a plan of the loading plunger and slide which, regulate the feeding
of the cartridges.
Figure 9 is a longitudinal section of the rear part through C, C; Figure 7:
Figure 10 is a longitudinal section through D, D, Figure 7.
Figure 11 is the interior view of the door: which closes the rear part of the

page_text: Figure 12 is a plan of a revolving cannon mounted on a universal pivot in the
act of being layed by the operator; Figure 13 is a side elevation of the same ;
Figure 14 is a section through E, E, Figure 13.
Figure 15 is a front view of a cartridge case; Figure 16 is a longitudinal section
of the same.
Figure 17 is a front view of the plate on which rest the firing pins of a French
mitrailleuse.
Figure 18 is a plan of a Swedish mitrailleuse; Figure 19 is a rear elevation of the
same; Figure 20 is a side elevation of the same.
Fignres 21 and 22 are diagrams representing the cone of dispersion of a common
piece of ordnance.
Figures 23 and 24 are diagrams representing the cones of dispersion of the re-
volving cannon.
Figure 25 is a sectional side view of the rear of a piece showing an arrangement
for operating the sight.
Figure 26 is a first modification of this arrangement.
Figure 27 is a second modification thereof; and Figure 28 is a third modification
thereof.
First Improvement.-The first improvement consists in so arranging the parts that
the separate barrels during the act of being fired rest exactly in the middle vertical
plane of the piece and in the lowest position. In all constructions known heretofore
the position of the barrel to be fired was in the highest position of this plane.
Figures 6, 7, and 9 represent the changes which this novel arrangement calls for in
the construction of the parts. The firing pin a has been placed in a lower position.
The principal advantage gained by this alteration is preventing the tendency of
the gun to lose its line of direction by the action of the discharge, which happens
if the firing barrel is not in the vertical plane passing through the axis. The in-
clined plane b, Figure 6, on which the heads of the cartridges slide along in the
act of turning the barrels, and which serves to force them into their proper places
for firing, can be made much longer than in any other construction known, thereby
the turning of the crank is greatly facilitated. The arm c extending from the firing
pin a, which is operated by the cam represented in Figure 9, can be made shorter
than ordinarily, and is therefore less liable to break.
Second Improvement.-It occurs sometimes that the operator in opening the door
which closes the rear part of the gun, accidentally loses his hold of the same. In
such case the cover will rapidly turn downward as far as the hinge allows. This
produces a considerable strain on the hinge, and has often been the cause of breakage.
To avoid this I propose to employ a brake on this part. In Figure 9 I have shown
a brake which consists in a piece d sliding freely in a suitable cavity provided in
the casting of the rear part of the piece. Two or more springs f properly arranged
serve to press the piece d against that part of the door which forms a part of the
hinge with sufficient force to produce so much friction as to keep the cover in any
position in which it may be left. I do not however confine myself to this mode of
construction, there being many other ways of accomplishing the same end.
Third Improvement.-I have arranged the parts of the mechanism of a revolving
cannon in such novel manner that the entire mechanism can be taken apart without
the aid of an instrument; for this purpose the crank h, through which motion is
imparted to the mechanism for loading and extracting, is fixed to the rear end of
the shaft g, Figures 7 and 10, by means of a thumbscrew i. As soon as this screw is
taken out all the moving parts may be taken out of the breech of the gun. First,
the crank shaft g is withdrawn, subsequently the crank h, worm k, the extractor l,
.or the loading plunger m. These parts can afterwards be replaced in the same order,
and the whole fixed by the screw i.
Fourth Improvement.-This part of the Invention relates to the mechanism of the
extractor. I have improved the shape of the groove o in which engages the pin of
the crank h. This groove has been generally made either straight or of a different
shape to the present. Figure 10 represents my improved shape, which is so curved

page_text: as to cause a longer period of rest in the motion of the extractor at each end of its
course. To make the extraction of the fired cartridge case absolutely positive I
make the extractor in form of a solid double hook, into which the rim of the
cartridge engages by the rotation of the barrels (heretofore it consisted of one solid
and one spring hook). The shell of the cartridge is thereby firmly held until it is
pushed out by the inclined plane p in the rear. To support the shell between the
hooks until it is entirely extracted from the chamber I provide a guide p', Figure 6,
on which it rests and is drawn along. This support is somewhat shorter than the
complete cartridge, so that the latter after being entirely extracted is at liberty to
fall readily to the ground. The inclined plane p only serves to disengage the shell
from the hooks if the shell should accidentally be retained between the hooks.
Fifth Improvement.-The mainspring represented in Figures 9 and 11 has been
improved in the following respects:-I have provided a square ring embracing both
arms of the spring, so as to keep the same under constant tension, and that it may
be introduced into its place already compressed. By these means I avoid the
necessity of compressing the spring when closing the rear door of the breech; but
this end may be obtained by other means, and I do not confine myself to the precise
construction represented. I have also so arranged the parts holding the spring in
place that the operator can easily take out and exchange the spring without any
tools; for this purpose I form the rear door with two flaps q, q, through which
passes the pin q', which holds the spring in place. This pin is formed with a feather
9, which is accomodated in the space between the two branches or arms of the
spring. In the lugs q² I provide a slot which corresponds in shape with the feather
of the q. When the spring is swung back into the position indicated in dotted
lines in Figure 11, the slot in the lug q³ allows the pin q' to be withdrawn. But in
any other position of the spring the feather q³ will obviously abut against the flap
and prevent the pin from falling out.
Sixth Improvement.-On the breech sight I have introduced transparent figures,
that is, I have cut the figures right through the metal, in order to make them easier
visible than the figures which are only engraved on the metal, as has been done
heretofore.
Seventh Improvement.-To enable the gunner to keep the fire of a revolving
cannon or machine gun continually directed on a moving object I mount the same
on a universal pivot, and provide the gun with a shoulder piece r and handle 8;
this handle being arranged in such a manner that while grasping the same with
his left hand the gunner can with his outstretched thumb stop the motion imparted
to the crank, and thus have time to lay the gun, the crank in that position being
immediately before the position for firing, which takes place by a slight further
forward motion of the crank. By means of the above-mentioned shoulder piece
and handle 8, in combination with the usual crank for firing, the gunner can at the
same time point and fire the piece, see Figures 12, 13, and 14. The peculiar
position of the crank represented in Figures 13, which I have adopted in com-
bination with the shoulder piece and the handle, are in the Drawing represented
as applied to a revolving cannon. It will be seen that they can with the same
result be attached to any machine gun. The shoulder piece may be firmly fixed to
the weapon, or may be made detachable. In this latter case I generally use a
spring catch, see Figure 12, with a button 1 extending through the metal; by
pressing upon this button the catch is disengaged, and the shoulder piece can be
dismounted by withdrawing it from its socket. Its length may be regulated to suit
the size of the gunner by a sliding arrangement, and set by means of a screw r¹,
or any other suitable means.
Eighth Improvement.-Revolving cannons of larger size, the mechanism of which
require considerable power to work, are generally so constructed that a single
revolution of the main shaft is effected through two or more revolutions of the
crank. This end may be obtained in different manners, for instance, through inter-
mittent gear wheels. I employ a signal, which at a short interval before the firing.
takes place gives a sign to the operator. This signal may be either an acoustic or

page_text: an optic one. In the Drawing, Figure 14, I have shown a bell t, which is struck
at the proper moment by a pin extending from the main shaft g.
Ninth Improvement. The cartridges are contained in what I term feed cases u.
In preparing for firing the operator inserts a case into the feed trough u¹, where-
upon the feed case is opened and the cartridges fall down into the feed trough u'.
I have devised means to automatically open the cover u² which confines the
cartridges in the case u, Figures 15 and 16. The cover u² is held in the closed
position by a turn button us. In inserting the case u into the feed trough, the end
of the turn button, which is turned outward and properly curved, is struck by the
curved edge u of the feed trough. Thereby the turn button is turned sufficiently
to set the cover u² at liberty, which by the weight of the cartridges is forced out-
ward, and allows the latter to fall down into the feeder. "I am well aware that
other automatic arrangements for this purpose have been proposed, but I consider
this arrangement superior, as it is worked without any spring.
11:
Plaft. …..
Tenth Improvement.
mprovement. My, revolving cannon as formerly constructed were pro-
vided with a swinging piece to regulate the introduction of the cartridges into the
receiver. This swinging piece was operated by the loading plunger. To admit a
cartridge from the feed trough into the receiver of the piece, the swinging piece
was turned down, and after the passage of one cartridge lifted again into the hori
zontal position, thus crowding back the rest of the cartridges in the feed trough.
It will be seen that considerable force was required for the operation of this swinging
piece, especially when the feed trough was full of cartridges. In quick firing the
rapid upward motion of the piece often caused the cartridges to be thrown out of
the feed trough. I have overcome this difficulty by substituting a horizontal sliding
piece, represented in Figures 6, 7, and 8, where it is marked v. It pivots in a
horizontal plane on a pin extending therefrom, and carries on its under face a
suitably shaped groove, in which works a pin extending from the fore-end of the
loading plunger. It will be seen that the longitudinal motion imparted to the
loading plunger m will cause the piece to swing horizontally on the pin v¹. The
groove in the piece v is so formed that when the loading plunger m has arrived at
the back end of its course the piece will be swung entirely to one side, thus
allowing a cartridge to fall down into the receiver; but as soon as the loading
plunger commences its forward motion to push that cartridge into the chamber the
piece will gradually be swung around, and interpose itself between the cartridges.
in the feed case and the one in the receiver without lifting the former ones to any
material extent. The entrance to the receiver will thus be closed, and prevents any
other cartridge entering until the proper moment.
'
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Eleventh Improvement. I have found by actual experiments that the angle of the
cone of dispersion of case or canister shot fired from rifled guns is determined by
the pitch of the rifling. I have also found that nearly all the balls fly on the
periphery or outside of this cone; these facts have proved to me the insufficiency of
common cannon used for flanking and similar purposes, and I have devised a method
to avoid this inefficiency by means of guns having several barrels. The difficulty.
experienced in covering a trench or ditch with canister shot consists in the fact
that the ditch cannot be properly covered by the dangerous zone of the cone of
dispersion. Figures 21 and 22 show an elevation and a plan of the position of the
cone of dispersion of an ordinary cannon in the ditch. There is a large space not
at all covered by the balls, and the enemy may pass with impunity in any part of
the ditch not covered by the dangerous zone of the cone of dispersion. Basing my
calculations on the above-mentioned fact, viz., that the course of the bullets in their
flight effects the form of a hollow cone, the angle of which depends on the
pitch of rifling, I overcome the difficulty by constructing a gun of more than one
barrel, so that the pitch of the rifling of each barrel is different from the pitch of
the rifling of the other barrels. Evidently the cone of dispersion of each barrel will
be different from that of the other barrels. With a gun thus constructed it is easy,
if the pitch of rifling of the barrels be properly determined, to cover a ditch in the
manner represented in Figures 23 and 24. In this case I would, for instance,
"

page_text: divide the trench to be flanked in six different zones a, b, c, d, e, f, and cover each
zone by a different barrel. Barrel No. 1 will produce a cone of dispersion which
will sufficiently cover the zone a; barrel No. 2
b; barrel No. 3.
. C,
and so forth. If the conditions be known it is easy with proper calculation to
cover with balls the entire prismatical space of a ditch. In trenches of great
length it may be necessary to give each barrel an independent elevation to suit the
cone of dispersion. For the revolving cannon I have devised the following means
to give every barrel its proper angle of elevation :-I form the rear disk w, Figures 1,
2, and 4, which carries and turns with the barrels, with a cam-shaped edge w¹.
This disk rests upon a fixed bearing w³, and being turned gives the gun the proper
elevation for each barrel. The same result may be obtained with a French
mitrailleuse by providing the plate which arrests the firing pins, Figure 17 (which
in the act of firing is moved sideways) on its lower face with an inclined plane x,
which, resting upon a fixed bearing or roller, properly lays the barrels for each
discharge. A Swedish mitrailleuse, Figures 18, 19, and 20, may be elevated by
pushing a wedge ¹ between the fixed parts of the piece and the part holding the
barrel together. This wedge z¹ may be pushed forward by the same lever z, which
is acted upon in discharging the barrels. There are many other methods than those
here mentioned to give a separate elevation to the gun for each barrel, and I do not
therefore confine myself to those described.
Twelfth Improvement. In order that the gunner may have entire control over
the laying, sighting, and firing of a Hotchkiss revolving cannon, or any other
machine gun trained in a similar manner as herein-before described with reference
to the Seventh Improvement, I have arranged the handle 8 so as to move by means
of the different peculiar arrangements hereafter described the sight up and down
at the same time that the gunner is working the piece, and which are shown in
Figures 25, 26, 27, and 28, which are sectional, longitudinal, and rear elevations
respectively of a revolving cannon or other similar gun.
The first arrangement, see Figures 14 and 25, consists in providing the handle s
with a pinion or teeth 1, which gears into a corresponding rack 2, which slides up
and down in any appropriate manner in the rear of the piece, and the upper end of
which forms the sight.
The second arrangement, see Figures 26 and 27, consists in imparting motion to
or operating the sight by means of a Galle chain or other equivalent chain 3 fitting
at one end on to a corresponding wheel or roller on the shaft, and the other end
being fastenened to the sight, which sight slides in a suitable cavity in the rear of
the piece. A suitable spring or other equivalent means 4 serves for keeping the
said sight constantly raised until acted on by the above-mentioned chain 3.
The third arrangement, see Figure 28, consists in realising the same end by means
of a screw and gearing. 5 is a bevel pinion fixed upon the handle 8, which gears
into a second similar pinion 6 fastened at the end of a screw 7 entering the sight from
below; thus, by turning the handle 8, motion will be transmitted from 5 to 6, and
from 6 to the sight, which is arranged so as to slide up and down in any suitable
manner.
I do not however limit myself to the above-described arrangements, as other
mechanisms fulfilling the same object may be made use of, such as a combination of
levers, etc.
I claim as new and desire to secure by Letters Patent,-
First. A revolving cannon so constructed that the discharge from each barrel is
effected when the axis of such barrel is in the middle vertical plane of symmetry of
the piece, and in its lowest position, as described, and for the purposes set forth and
shown.
Second. A brake operating on a door, which closes the rear part of a revolving
cannon, for the purposes herein set forth.
Third. A revolving cannon so constructed that the mechanism in the rear can be
taken apart and remounted without the aid of tools, as above described.

page_text: Fourth. In a revolving cannon the improved cam 1'having a groove of a form
substantially as shown.
Fifth. The double-hooked extractor in combination with the supporting plane p¹
and wedge-shaped. plane or ejector p, substantially as shown, and for the purposes
set forth.
Sixth. In a revolving cannon, the improved method of attaching the mainspring,
also a ring embracing the arms of the mainspring, or other similar means giving
the same result; substantially as shown and described, and for the purpose set
forth.
Seventh. The transparent numbers on the back sight of fire-arms, as and for the
purpose set forth.
Eighth. A revolving cannon or. machine gun having a fixed. or a detachable
shoulder piece, with the peculiarly arranged crank, substantially as shown and
described, and for the purposes set, forth.
Ninth. A revolving cannon provided with an acoustic or optic signal, as and for
the purposes set forth.
Tenth. A feed case for revolving cannon having an automatic arrangement for
opening, the same in the act of being inserted into the feeder of the piece, as shown,
and for the purpose set forth.
Eleventh. A revolving cannon having a horizontal pivotting piece, which regulates
the admission of the cartridges to the receiver, substantially as shown, and for the
purposes set forth.
Twelfth. A piece of ordnance having several barrels, which barrels are so rifled
that the pitch of the rifling of each barrel is different from that of one, several, or
all the others, or one or more may be smooth-bored, also means for automatically
giving to the separate barrels separate angles of elevation for firing, for the purposes
herein set forth.
Thirteenth. A sight so constructed that it can be worked by the handle under-
neath the breech, substantially as above described, and for the purposes set
forth..
In witness whereof, I, the said William Morgan-Brown, have hereunto set my
hand and seal, this Thirtieth day of July, in the year of our Lord One
thousand eight hundred and seventy-eight.
WILLIAM MORGAN-BROWN. (L.S.)