An Improvement in Breech Plugs for Ordnance.
Year: 1895

page_text: Date of Application, 16th Apr., 1895-Accepted, 24th May, 1895
COMPLETE SPECIFICATION.
An Improvement in Breech Plugs for Ordnance.
I, DOUGLAS VICKERS, a Managing Director of Vickers Sons & Company
Limited of River Don Works Sheffield 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 screw of the plug for closing the breech of a gun is usually made in segments
separated by blank spaces, so that the locking or unlocking of the threads of the
plug is effected by a partial turn.
It has been proposed also to make the plug in steps of varying radius, and of such
a depth, that the locking or unlocking is also effected by a partial turn, but only one
blank space is required.
When the screw plug is made according to either of these methods, it is necessary
before locking or after unlocking the threads, that the plug should slide rectilineally
and as it is usually mounted on an arm pivotted at the side of the gun, three
successive movements are required to close or open the breech; to close it the first
movement is to swing the arm on its pivot, the second to slide the plug rectilineally,
and the third to turn it partially round to lock the threads; to open the breech the
same movements have to be made in reverse order.
My invention relates to the construction of a screw plug of the varying radius
type above referred to in such a manner that no rectilineal sliding motion of the
plug is necessary, and thus only two motions are required in closing or opening the
breech, to close the breech, the first movement is to swing the arm on its pivot and
the second is to turn the plug partially round to lock the threads, as I shall describe
referring to the accompanying drawings.
Fig. 1 is a transverse section of the breech and the plug, the latter in its unlocked
position.
Fig. 2 is a sectional plan on the line Z Z of Fig. 1.
P is the pivot on which the arm carrying the breech plug is mounted. The
radii of the several steps of the threads and of the blank spaces on the plug and in
the breech are such that they form sufficient clearance at each step, so that on
swinging the screw plug on the arm around P as a centre, the threads and spaces of
the screw plug clear the threads and spaces in the breech.
As shewn in Fig. 1 the threads are made in three symmetrical pairs of steps, those
of the greatest radius A, of the next radius A¹, and of the least radius A³ but
obviously there might be a different number of steps. B and C indicate the spaces
in the breech and E, F the spaces on the plug, the dotted lines indicate the bottoms
of the screw threads.
When the screw plug stepped as shewn in Fig. 1 is turned one eighth of a
revolution, A engages with a, A' with a' and A with a². When the plug is in
the position shewn in Fig. 1, it can be swung on the pivot P, A clearing B, and C,
A clearing a, A' clearing a', and E, and F, clearing a².
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
The construction of a breech plug for a gun in several segments and steps so

page_text: arranged and proportioned that the breech plug can be swung in a circular path
around the pivot on which the arm carrying it is mounted, substantially as
described.
ABEL & IMRAY,
Agents for the Applicant.