IMPROVEMENTS IN APPARATUS FOR FACILITATING THE EXAMINATION AND REPAIRS OF THE SUBMERGED PARTS OF SHIPS OR VESSELS
Year: 1872

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn
Fields, in the County of Middlesex, Gentleman, for the Invention
of "IMPROVEMENTS IN APPARATUS FOR FACILITATING THE EXAMINATION AND
REPAIRS OF THE SUBMERGED PARTS OF SHIPS OR VESSELS." -A communi-
cation from abroad by John Inglis, of Hong Kong.
Sealed the 10th October 1872, and dated the 27th April 1872.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson
at the Office of the Commissioners of Patents, with his Petition, on
the 27th April 1872.
°
I, JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the
County of Middlesex, Gentleman, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN APRARATUS FOR FACILITATING THE
EXAMINATION AND REPAIRS OF THE SUBMERGED PARTS OF SHIPS OR VESSELS," a
communication to me from abroad by John Inglis, of Hong Kong, to be
as follows:-
This Invention relates to certain peculiar constructions and arrange-
ments of portable cofferdams adapted to fit against the sides and the

page_text: bows or stern of a ship or vessel, for the purpose of examination,
cleaning, or repairs of those parts which are submerged without the.
necessity for putting the ship into dry dock.
In constructing a portable, flexible cofferdam suitable for application
to the sides or bottom of a ship or vessel, I take a number of semicircular
or semi-elliptical iron bows or curved stretchers, having eyes in their
extremities which I attach to flexible brass or copper chains, being
kept at right angles thereto by suspension chains; iron stays across
the bows at intervals strengthen them against the pressure of the
water. These bows and the intervening spaces are covered with a
waterproof hood or trunk, preferentially composed of two thicknesses
of oiled canvas with. a solution of india-rubber between, but otherwise
of any strong and waterproof material. This is constructed in sections
somewhat like those of a balloon so as to allow of expansion at the
back of the trunk when applied to a circular object, such as the sides
of a ship. Bolts and nuts secure this hood or trunk to the flexible
chains, while fork bolts and nuts secure it to the bows. The cloth
composing the hood is turned round the flexible chains inward, the
inner edge being first sewn and then cemented to the outer portion,
thus completely covering and hiding the chains. The bottom is of
wood with a moveable edge composed of moveable segments of wood
kept in position by a powerful india-rubber spring, and capable of
adjusting itself to any horizontal curve. Attached by rivets and india-
rubber cement to the front face of the cloth covered chain is a band
of rubber which extends all round the perpendicular and bottom edges
of the trunk. Outside this again comes a hollow oblate rubber pipe
which acts as a waterproof flange to give close adhesion to the ship's
side. This pipe can be connected with an hydraulic pump at its upper
end, and so be made additionally tight by being distended. This how-
ever is not always necessary.
The segments of wood above mentioned work between the bottom
and a piece of wood or metal secured by screws at the corners.
A pet
⚫ cock allows the water to be readmitted after being pumped out of the
trunk in order to detach it from the ship's side.
Suitable tackles and purchase falls are employed for haulling the
apparatus against the ship's side, or curved metal bars bent to a semi-
aisoules Ciolent shane

page_text: 'The apparatus which I propose to apply to the stem or stern of a ship,
for the repair of a screw propeller for example, consists of a floating
chamber constructed of sheet iron suitably stayed within, and made
double at its bottom and sides, the space between the inner and outer
skin forming a series of water-tight compartments. Round the upper
edge of the three sides a hollow pontoon is formed, and upon this joining
the edge of the floating chamber is placed a strong wooden platform
protected by rails. Valves are so placed in both the floating chamber
and pontoon as to permit the ingress of water to any desired extent;
while other valves permit the said water to be ejected from the chamber
and pontoon by means of an ordinary Downton or other pump.
At the open end of the floating chamber there are placed two gates
opening upon hinges and shutting against the sill of the chamber. A
strip of waterproof material covering both the edge of the floating
chamber and the hinge edge of the gates makes a connection between
them impervious to water. The curved edge of the gates consists of a
moveable india-rubber flanging which by means of hydraulic rams is
forced with sufficient strength against both sides of the vessel to which
the cofferdam is applied to serve as a water-tight barrier. The several
bydraulic rams are fed from a perpendicular pipe having a series of
shorter pipes or cylinders screwed to it. Each of these short pipes is
constructed to admit a close fitting ram, hydraulic pressure being
applied to the series simultaneously by means of an ordinary hydraulic
pump. Upon the face of these rams comes a flexible chain bolted and
cemented to rubber bands on its front and sides. This chain is fastened
to a tube and is connected with a moveable rod capable of being
protruded or withdrawn by a screw movement worked by a winch
handle. A coat of waterproof material, loose enough to permit of
the flange being pushed out to whatever extent and in whatever curve
may be necessary, extends from the edge of the flange to the body
of the gate which is formed of wooden chocks between the pipes with
an outer scantling on either side. Outside either flange is a rubber
pipe which serves to give adhesion to the gates and form a water-tight
joint. It is distended from an bydraulic pump attached to a tube to
make it fit accurately.
In the centre of the floating chamber and in contact with the inner
sides of the gates when closed is an hydraulic bellows, also provided
with a rubber flange and connected with a pump by which it can be

page_text: forced up to the height necessary for pressing against the keel of the
vessel placed in the chamber, and so preventing the ingress of water in
that direction. In front of it is a rubber apron which bears against the
gates so as to form a water-tight joint.
Water having been admitted through the valves until the chamber is
sunk to about a foot above the surface, the chamber is then floated to
the stern of the vessel to which it is to be applied, and the gates being
opened so as to be in a line with or parallel to the sides, the chamber is
pushed with the open end forward till the after platform is about in a
line with the traffrail, thus bringing the stern inside the said chamber.
The gates are then closed. Tackles from each corner of the platform
are then attached to the ship and hauled taut. The water from the
pontoons is then pumped out, and if this gives sufficient floating power
to bring the hydraulic bellows against the keel the tackles are merely
hauled well taut, and the pump being connected to the. bellows its
flange is forced well up. If on the other hand it is necessary that the
pontoon rise higher, water must be pumped from the lower air chambers.
So soon as the bellows grips the purchases must be tautened as much
as possible. The hydraulic pumps are then kept going until the in-
creased tension on the tackles shews that the gate flanges are pressing
hard on the sides. The sucker tube is then connected with the pump
and distended until it appears that it has filled up every chink between
the flanges and the ship on either side. The floating chamber is then
emptied of water and a dry cofferdam is thus formed, within which the
necessary repairs may be executed.
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 26th October 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of
Middlesex, Gentleman, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-seventh day of April, in the year
of our Lord One thousand eight hundred and seventy-two, in the thirty-

page_text: fifth year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said John Henry Johnson, Her special.
license that I, the said John Henry Johnson, my executors, adminis-
trators, and assigns, or such others. as I, the said John. Henry Johnson,; ·
| my executors, administrators, or assigns, should at any time agree with,-
and no others, from time to time and at all times thereafter during
the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention for
"IMPROVEMENTS IN APPARATUS FOR FACILITATING THE EXAMINATION AND REPAIRS
OF THE SUBMERGED PARTS OF SHIPS OR VESSELS," a communication to me
from abroad by John Inglis, of Hong Kong, upon the condition
(amongst others) that I, the said John Henry Johnson, my executors or
administrators, by an instrument in writing under my hand and seal,
should particularly describe and ascertain the nature of the said In-
vention, and in what manner the same was to be performed, and cause
the same to be filed in the Great Seal Patent Office within six calendar
months next and immediately after the date of the said Letters Patent.
"
NOW KNOW YE, that I, the said John Henry Johnson, do hereby
declare the nature of the said Invention, and in what. manner the ;
same is to be performed, to be particularly described and ascertained.
in and by the following statement, reference being had to the accom-
panying Drawings and to the letters and figures marked thereon, that
is to say:-
The said Invention relates to certain peculiar constructions and
arrangements of portable cofferdams adapted to fit against the sides
and the bows or stern of a ship or vessel for the purpose of examination,
cleaning, or repairs of those parts which are submerged without the
necessity for putting the ship into dry dock.
In constructing a portable flexible cofferdam suitable for application
to the sides or bottom of a ship or vessel, I take a number of semi-
circular or semi-elliptical iron bows or curved stretchers having eyes in
their extremities, which I attach to flexible brass or copper chains, being
kept at right angles thereto by suspension chains. Iron stays across the
bows at intervals strengthen them against the pressure of the water.
These bows and the intervening spaces are covered with a waterproof
hood or trunk, preferentially composed of two thicknesses of oiled

page_text: canvas with a solution of india-rubber between, but otherwise of any
strong and waterproof material. This is constructed in sections some-
what like those of a balloon, so as to allow of expansion at the back of
the trunk when applied to a circular object, such as the sides of a ship.
Bolts and nuts secure this hood or trunk to the flexible chains, while
fork bolts and nuts secure at the bows. The cloth composing the hood
is turned round the flexible chains inwards, the inner edge being first
sewn and then cemented to the outer portion, thus completely covering
and hiding the chains. The bottom is of wood, with a moveable edge
composed of moveable segments of wood, kept in position by a powerful
india-rubber spring, and capable of adjusting itself to any horizontal
curve. Attached by rivets and india-rubber cement to the front face of
the cloth covered chain is a band of rubber, which extends all round the
perpendicular and bottom edges of the trunk. Outside this again comes
a hollow oblate india-rubber pipe, which acts as a waterproof flange to 1
give close adhesion to the ship's side. This pipe can be connected with
an hydraulic pump at its upper end, and so be made additionally tight
by being distended. This however is not always necessary.
The segments of wood above mentioned work between the bottom and
a piece of wood or metal secured by screws at the corners. A pet cock 2
allows the water to be re-admitted after being pumped out of the trunk
in order to detach it from the ship's side.
Suitable tackles and purchase falls are employed for hauling the
apparatus against the ship's side.
The apparatus which I propose to apply to the stem or stern of a ship a
for the repair of the screw propeller for example, consists of a floating
chamber or hydraulic cofferdam, constructed of sheet iron, suitably
stayed within, and made double at its bottom and sides, the space
between the inner and outer skin forming a series of water-tight com-
partments. Round the upper edge of the three sides runs an ovoid and 3
hollow pontoon, and upon this joining the edge of the floating chamber
is placed a strong wooden platform protected by rails.
Valves are so
placed in both the floating chamber and pontoon as to permit the
ingress of water to any desired extent, while other valves permit the said
water to be ejected from the chamber and pontoon by means of an a
ordinary Downtou or other pump.

page_text: At the open end of the floating chamber there are placed two gates
opening upon hinges and shutting against the sill of the chamber. A
strip of waterproof material covering both the edge of the floating
chamber and the hinge edge of the gates makes a connection between.
them impervious to water. The curved edge of the gates consists of a
moveable india-rubber flanging, which by means of hydraulic rams is
forced with sufficient strength against both sides of the vessels to which
the cofferdam is applied to serve as a water-tight barrier. The several
hydraulic rams are fed from a perpendicular pipe, having a series of
shorter pipes or cylinders screwed to it. Each of these short pipes is
constructed to admit a close fitting ram, hydraulic pressure being applied
to the series simultaneously by means of an ordinary hydraulic pump.
Upon the face of these rams comes a flexible chain, bolted and cemented
to rubber bands on its front and sides. This chain is fastened to a tube,
and is connected with. a moveable rod capable of being protruded or
withdrawn by a screw movement worked by a winch handle. A coat of
waterproof material, loose enough to permit of the flange being pushed
out to whatever extent and in whatever curve may be necessary, extends
from the edge of the flange to the body of the gate, which is formed of
wooden chocks between the pipes, with an outer scantling on either side.
Outside either flange is a rubber pipe, which serves to give adhesion to
the gate and form a water-tight joint. It is distended from an hydraulic
pump attached to a tube to make it fit accurately.
"
In the centre of the floating chamber, and in contact with the inner.
sides of the gates when closed, is an hydraulic bellows or ram, also pro-
vided with a rubber flange and connected with a pump, by which it can
be forced up to the height necessary for pressing against the keel of the
vessel placed in the chamber, and preventing the ingress of water in that
direction. In front of it is a rubber apron, which bears against the gates
so as to form a water-tight joint.
Water having been admitted through the valves until the chamber
floats only about a foot above the surface it is taken to the stern of the
vessel to which it is to be applied, and the gates being opened till in a
line with the sides is pushed with the open end forward till the after
platform is about in a line with the taffrail. The gates are then closed,
and tackles from each corner of the platform are attached to the ship
and hauled taut. The water from the pontoons is then pumped out, and
if this gives sufficient floating power to bring the hydraulic bellows or

page_text: ram against the keel, the tackles are merely hauled well taut, and the
pump being connected to the bellows or ram its flange is forced well up.
If, on the other hand, it is necessary that the pontoon should rise higher,
water must be pumped out of the lower air chambers. So soon as the
bellows or ram grips, the purchases must be made as taut as possible. 5
The hydraulic pumps are then kept going until the increased tension on
the tackles shews that the gate flanges are pressing hard on the sides.
The sucker tube is then connected with the pump, and distended until it
appears that it has filled up every chink between the flanges and the
ship on either side. The floating chamber is then emptied of water, and 10
a dry cofferdam is thus formed within which the necessary repairs may
be executed.
And in order that the said Invention may be fully understood I
shall now proceed more particularly to describe the same, and for that
purpose shall refer to the several Figures on the annexed two Sheets of 1
Drawings, the same letters of reference indicating corresponding parts in
all the corresponding Figures.
Fig. 1 (Sheet 1) of the Drawings represents a vertical section and
partial side elevation of the flexible cofferdam; Fig. 2 is a corre-
sponding front elevation of the open side thereof; Fig. 3 is a plan 20
corresponding to Fig. 1; and Fig. 4 is a view showing the mode of
applying the said flexible cofferdam to the side of a ship.
In constructing the improved flexible cofferdam a certain number of
sections, according to the depth required, each consisting of 5 or more
semicircular or semi-elliptical iron bows, having eyes A in their extremi- 2
ties, are attached to a flexible brass or copper chain B, and kept at right
angles thereto by the chains C, C. Iron stays D across the hows at
intervals strengthen them against the pressure of the water. These
bows and the intervening spaces are covered with a waterproof hood or
trunk E, preferentially composed of two thicknesses of oiled canvass 30
with a solution of india-rubber between, but otherwise of any strong and
waterproof material. This is constructed in sections somewhat like those
of a balloon, so as to allow of expansion at the back of the trunk when
applied to a circular object (sec Fig. 4); brass or iron bolts with nuts
(prolonged to carry metal sheaves and guards F, F,) secure this hood or 3
trunk to the flexible chain B. The bow at the lower end of each section
is made of flat bar iron, so as to fit over that at the upper end of the

page_text: section below it, as shewn at A' in Fig. 1, and the two are secured as
a water-tight joint by a series of thumb screws or screw bolts and
butterfly nuts, as shewn at b, b (Figure 1). The cloth composing the
liood is turned round the flexible chain inwards, the inner edge being
first sewn and then cemented to the outer portion, thus completely
covering and hiding the chain. The bottom G, Figs. 1 and 3, fitted to
the lower end of a section is of wood with an adjustable edge con-
sisting of wood, brass, or metal segments c, c, pressing on a rubber
spring H, and covered with a waterproof apron on both sides of the
bottom capable of adjusting itself to any horizontal curve. Attached by
rivets and india-rubber cement to the front face of the cloth covered
chain is a band of rubber I, which extends all round the perpendicular
and bottom edges of the trunk. Outside this again comes a hollow
oblate rubber pipe K passed down the edge of the trunks through the
bands L, according to the number of sections used, which pipe acts as a
waterproof flange to give close adhesion to the ship's side. This pipe is
connected with an hydraulic pump at its upper end, and is made addi-
tionally tight by being distended.
•
The segments c, c, above referred to work between the bottom G and
a piece of wood or metal M (Figure 1) attached by screws or otherwise
to G. A valve N or a pet cock allows the water to be readmitted after
being pumped out of the trunk, in order to detach it from the ship's
side. Adhesion to the ship's side is secured by ropes passing on both
sides of the trunk over the sheaves Finside the guards, and connected
to a span rope or chain passing under the ship's keel, hauled taut on
the opposite side, and bowsed-to by tackles on either side of the mouth
of the trunk. O is a pontoon for floating the flexible cofferdam.
Fig. 1 on Sheet 2 of my Drawings is a longitudinal vertical section of
the improved hydraulic cofferdam to be applied to the bows or stern
of a ship; Fig. 2 is a corresponding plan of the same; Fig. 3 is an
elevation and partial transverse section of the open end of the said coffer-
dan. The rest of the Figures are details which I shall herein-after
refer to.
This cofferdam may be square or oval shaped, and is so constructed as
to float at various depths as may be required, and has at its open end

page_text: A is a floating chamber open at one end, constructed of sheet iron
suitably stayed within and double at its bottom and sides, the distance
between the inner and outer skin, which form a series of water-tight
compartments, varying from 1 foot to 3 feet according to dimensions and
capacity. Round the upper edge of the three sides are fitted three ovoid
and hollow pontoons B, and upon these joining the edge of the floating
chamber, is placed a strong wooden platform C, protected by rails if
desired. Valves D, which may be of Kingston's or other pattern, as
shewn in Drawings, are so placed in both the floating chamber and
pontoon as to permit the ingress of water to any desired extent, while
the pipes E each provided with a stop-cock, permit the said water to be
withdrawn from the chambers and pontoons by means of an ordinary
steam, Downton, or other pump, such pipes leading to one common
exhaust chamber F. At the open end of the floating chamber A, there
are placed two gates G, G, opening upon hinges at H, H, and shutting
to against the sill I (Figure 8). A strip of waterproof material a covering
both the edge of the floating chamber and the hinge edge of the gates,
makes a connection between them impervious to water. The curved
edge of the gates consists of a flexible chain J (Figures 4 and 5), covered
with india-rubber flanging 6, outside of which is attached a dilatable
pipe C of the same material, and outside this pipe a layer of "thrum-
ming" d is applied, the whole of which by means of hydraulic cylinders
and rams K, as shewn in Figure 3, is forced with sufficient strength
against both sides of the vessel to which the cofferdam is applied to
serve as a water-tight barrier.
In Figure 3, L is a perpendicular pipe having a series of shorter pipes
or cylinders K secured to it. Each of these short pipes or cylinders is
constructed to admit a close fitting ram, hydraulic pressure being applied
to the series simultaneously by means of an ordinary hydraulic pump
attached to the pipe L at e. Upon the face of these rams bears the
flexible chain J bolted and cemented to rubber bands on its front and
sides. This chain is fastened to the tubo L at f, but is connected at g
with a movable rod M (see Figure 7), capable of being protruded or
withdrawn by a screw movement worked by the winch handle N, as
shown in enlarged detail in Figure 6. A sheet h of waterproof material
loose enough to permit of the flange being pushed out to whatever
extent, and in whatever curve may be necessary, extends from the edge
of the flange to the body of the gate (see Fig. 3), which body is formed

page_text: of wooden chocks between the pipes or cylinders K with an outer scant-
ling on either side. Outside either flange is the dilatable rubber pipe c,
with cloth or other thrumming attached, which serves to give adhesion
to the gates and form a water-tight joint. The pipe is distended from an
hydraulic pump connected therewith at i when required to make it fit
accurately.
In the centre line of the floating chamber, and in contact with the
inner sides of the gates when closed is an hydraulic piston O (Figs. 9
and 10) provided with a rubber, metal, or rubber covered metal flange,
and connected with a pump by which it can be forced up to the height
necessary for pressing against the keel of the vessel placed in the
chamber, and so preventing the ingress of water in that direction. In
front of it is a rubber covered metal apron P, which bears against the
gates so as to form a water-tight joint.
The mode of applying the hydraulic cofferdam is as follows:-Water
having been admitted through the valves D. until the chamber floats
only about a foot above the surface of the water, it is taken to the stern
of the vessel to which it is to be applied, and the gates G being opener
till in a line with the sides is pushed with the open end forward till
the after platform is about in line with the taffrail. The gates G are
then closed by the tackles Q. Other tackles from each corner of the
platform C are then attached to the ship and hauled taut. The water
from the pontoons is then pumped or exhausted out, and if this gives
sufficient floating power to bring the hydraulic piston O against the keel
the tackles are merely hauled well taut, and the pump being connected
to the piston O its flexible flange R is forced well up and expanded by
forcing air therein through the pipe S (Fig. 9). If on the other hand
it is necessary that the pontoon rise higher, water must be pumped
from the lower air chambers so soon as the piston head and flange R
grip; the purchases must be tautened as much as possible. The
hydraulic pumps in connection with the pipes L, the air cocks K
of which must be opened, are kept going until the increased tension
on the tackles shews that the gate flanges are pressing hard on the
sides. The packing tube C is then connected with the pump and
distended until it appears that it has filled up every chink between the
flanges and the ship on either side. The floating chamber is then
emptied of water and a dry cofferdam is thus formed, within which the
necessary repairs may be executed..

page_text: The gates may be made of any required shape to fit whatever section
of the vessel may be deemed necessary, the essential details remaining
unaltered, or instead of gates the front portion of the cofferdam may be
constructed to carry hydraulic rams with flexible chain and flange to
serve the same purpose.
Having now described and particularly ascertained the nature of the
said Invention, and the manner in which the same is or may be used or
carried into effect, I would observe in conclusion that what I consider to
be novel and original, and therefore claim as the Invention secured to
me by the hercin-before in part recited Letters Patent is,—
First. The herein-before described peculiar flexible trunk forming a
portable cofferdam constructed in sections fitting into each other by
water-tight joints, the said trunk being floated and capable of being
towed into position for the purposes in view.
Secondly. The combination with the chains, bows, stretchers, and edge ]
packing of a waterproof covering made expansible at the portion furthest
from the ship's side, so as to follow the curve required, and keep the
iron bows forming the skeleton frame invariably at right angles to the
ship's side, substantially as and for the purposes herein-before described
and illustrated on Sheet 1 of the Drawings hereunto annexed.
Thirdly. The application of the moveable or adjustable edge fitted to
the bottom of the trunk, whereby it is made to adjust itself and fit any
curve of the vessel horizontally, ŝubstantially as herein-before described
and illustrated by the Drawings hereunto annexed.
5
Fourthly. The application of hydraulic machinery to gates working at
one end of a floating cofferdam built in water-tight compartments, or
to a part or parts of the said cofferdam occupying the position of the
gates, and to the bottom of the said cofferdam at the junction of the
gates, for the purpose of making a water-tight compartment exterior to
a vessel with a view to repairing or inspecting the same, substantially as a
herein-before described and illustrated in Sheet 2 of the Drawings here-
unto annexed.

page_text: manner and for the purposes herein-before described and illustrated on
Sheet 2 of the Drawings hereunto annexed.
In witness whereof, I, the said John Henry Johnson, have to this
my Specification set my hand and seal, the Twenty-fifth day
of October One thousand eight hundred and seventy-two.