IMPROVEMENTS IN OR APPLICABLE TO ARMOUR PLATES
Year: 1876

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LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in the
County of Middlesex, Gentleman, for the Invention of "IMPROVEMENTS IN
OR APPLICABLE TO ARMOUR PLATES." A communication from abroad by
the Firm of Marrel, Brothers, of Rive de Gier (Loire), in the Republic of
France, Iron Masters.
Sealed the 27th February 1877, and dated the 21st November 1876.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson 'at the
Office of the Commissioners of Patents on the 21st November 1876.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN OR APPLICABLE TO ARMOUR PLATES." A com-
munication from abroad by the Firm of Marrel, Brothers, of Rive de Gier (Loire),
in the Republic of France, Iron Masters.
This Invention consists in the application to armour plates of every description
constructed of steel or any other suitable metal, of blades, ridges, or bars of
tempered or hardened steel or other metal harder than the projectile which strikes
them.
In carrying out this Invention the blades, ridges, or bars of tempered or
hardened steel or other hard metal are made in the form of prisms of triangular
section and are fitted with a dovetail and let into the external surface of the plate,
so that when the projectile strikes upon the projecting edge of such blades, ridges, or
bars, which are much harder than the projectile itself, the projectile will be divided
into several pieces and will consequently lose a portion of its power of penetration,
or that if on the contrary it strikes one of the oblique sides of the blades, ridges, or
bars, not being able to take effect on the hard metal it will be caused to deviate.
from its course and in this case will likewise lose its power of penetration, which is
the essential object to be attained.
The form and mode of arranging the blades, ridges, or bars may be varied as
required; they may be constructed of rounded prismatic or angular forms as desired,
the number and dimensions of the same may also be varied, and they may be placed
in the direction in which the plate is rolled in order that they may not be broken

page_text: transversally by the process, which is of the greatest importance to the result
in view.
When the plates are destined to be attached to the sides of a ship the projecting
blades, ridges, or bars of hard steel are arranged longitudinally or in the direction of
motion of the vessel so that they do not offer any resistance to its progress; if on
the contrary they are intended to cover the turrets or other constructions situate
upon the decks of vessels or forts on land, the blades, ridges, or bars are placed
vertically in order that they may be situate in the direction of the rectilineal
generators of the plates which are curved in this case. The plates may be made of
a flat or curved form, and also be provided with ribs or webs if desired.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said John Henry Johnson in the Great Seal Patent Office on the 16th
May 1877.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN OR APPLICABLE TO ARMOUR PLATES." A com-
munication from abroad by the Firm of Marrel, Brothers, of Rive de Gier (Loire), in
the Republic of France, Iron Masters.
The said Invention consists in the application to armour plates of every
description constructed of steel or other suitable metal, of blades, ridges, or bars
designated "projectile breakers," composed of tempered or hardened steel or other
metal harder than the projectiles to be used against thein.
And in order that the said Invention may be fully understood I shall now pro-
ceed more particularly to describe the same, and for that purpose shall refer to the
several Figures on the annexed Sheet of Drawings, the same letters of reference
indicating corresponding parts in both the Figures.
Figure 1 of the accompanying Drawings represents a front clevation of an armour
plate with the said Invention applied thereto; and Figure 2 is a transverse section
of the same.
a is the plate which is provided with blades, ridges, or bars a¹ of steel
tempered to the hardness of tool steel. In the example shewn in the Drawing these
blades, ridges, or bars, are made in the form of prisms of triangular section, and are
fitted with a dovetail and let into the external face of the plate a, so that when the
projectile strikes upon the projecting edge of the said blades, ridges, or bars, which
are much harder than the projectile itself, the projectile will be divided into several
pieces and will consequently lose a portion of its power of penetration, or that if on
the contrary it strikes one of the oblique sides of the blades, ridges, or bars, not
being able to take effect on the hard metal it will be caused to deviate from its
course, and in this case will likewise lose its power of penetration, which is the
essential object to be attained.
The form and mode of arranging the blades, ridges, or bars a¹, may be varied as
required, they may be constructed of rounded prismatic or angular forms as desired,
the number and dimensions of the same may also be varied, and they may be placed
in the direction in which the plate is rolled in order to obviate the liability of their
being broken transversely by the process, which is of the greatest importance to the
result in view.
When the plates are intended to be attached to the sides of a ship the projecting
blades, ridges, or bars of hard steel are arranged longitudinally or in the direction
of the motion of the vessel so as not to offer any resistance to its progress; if, on the
contrary, they are intended to cover the turrets or other structures situate upon the
decks of vessels or forts on land, the blades, ridges, or bars are, for the convenience
of fitting, placed vertically, that is to say, they are situate in the direction of the
rectilineal generators of the plates, which in this case are curved.
Having now described and particularly ascertained the nature of the said Inven-
tion, and the manner in which the same is or may be used or carried into effect, I

page_text: would observe in conclusion that what I consider to be novel and original, and
therefore claim as the Invention secured to me by the herein-before in part recited
Letters Patent is the application to armour plates of blades, ridges, or bars of
tempered or hardened steel or other metal harder than the projectiles to be used
against them, substantially as and for the purposes herein-before described.
In witness whereof, I, the said John Henry Johnson, have to this my Specification
set my hand and seal, this Fifteenth day of May, One thousand eight hundred
and seventy-seven.
J. HENRY JOHNSON. (L.S.)