IMPROVEMENTS IN CAISSONS OR APPARATUS TO FACILITATE THE BUILDING OF BRIDGE PIERS AND SIMILAR STRUCTURES UNDER WATER
Year: 1869

page_text: LETTERS PATENT to Andrew Mitchell, of Leith, in the County of
Mid Lothian, North Britain, for the Invention of "IMPROVEMENTS IN
CAISSONS OR APPARATUS TO FACILITATE THE BUILDING OF BRIDGE PIERS AND
SIMILAR STRUCTURES UNDER WATER."
Sealed the 27th May 1870, and dated the 2nd December 1869.
PROVISIONAL SPECIFICATION left by the said Andrew Mitchell at
the Office of the Commissioners of Patents, with his Petition, on
the 2nd December 1869.
I, ANDREW MITCHELL, of Leith, in the County of Mid Lothian,
North Britain, do hereby declare the nature of the said Invention for
IMPROVEMENTS IN CAISSONS OR APPARATUS TO FACILITATE THE BUILDING OF
BRIDGE PIERS AND SIMILAR STRUCTURES UNDER WATER," to be as follows, that
is to say:
This Invention has for its object to facilitate the building of bridge
piers and similar structures under water; and it consists in employing
caissons which are U shaped horizontally, and one modification of which
comprises a pair connected together to form what may be termed a

page_text: bi-valve caisson. Such bi-valve caisson surrounds or encloses the space
in which the pier is to be constructed, and when the pier is built up to
the water level the parts may be separated or opened and the whole be
withdrawn and floated away from the pier.
The caisson is to be constructed of wrought-iron plates upon a framing
of angle iron and with a chamber or chambers on its outer side for
floating it and for receiving water or other ballast as required. The
vertical joint surfaces where the two parts meet are to be formed of
wood grooved to receive rubber, and the parts are to be held together by
clamps and screws during the building of the pier, at which time the
water is of course pumped out of the interior. The lower part of the
caisson is made with single plates to sink into the mud, and the con-
tinuation of the vertical joints between these plates are formed by
entering the edges of the plates on one side into angular grooves in the
other plates, in which grooves rubber is applied. The caisson is furnished
with shores at the sides to steady it, particularly when the bottom is
uneven, these shores being arranged to be screwed or otherwise forced
down separately, so that each may bear fully on the bottom. In some
cases whilst one of the caissons of a pair is U shaped the other may be
straight or nearly so.
In building continuous piers or walls sections may be first constructed
at short intervals by means of the bi-valve caissons, and then for filling
up each interspace two U shaped caissons may be used, one on each side
of the line of wall, and fixed up against the finished parts adjacent to
the interspace.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Andrew Mitchell in the Great Seal Patent Office on
the 2nd June 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ANDREW.
MITCHELL, of Leith, in the County of Mid Lothian, North Britain, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Second day of December, in the year.
of our Lord One thousand eight hundred and sixty-nine, in the thirty.,
third year of Her reign, did, for Herself, Her heirs and successors, give, a

page_text: and grant unto me, the said Andrew Mitchell, Her special licence
that I, the said Andrew Mitchell, my executors, administrators, and
assigns, or such others as I, the said Andrew Mitchell, my executors,
administrators, and 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
CAISSONS OR APPARATUS TO FACILITATE THE BUILDING OF BRIDGE PIERS AND
SIMILAR STRUCTURES UNDER WATER," upon the condition (amongst others)
that I, the said Andrew Mitchell, my executors or administrators,
by an instrument in writing under my, or their, or one of their.
hands and seals, should particularly describe and ascertain the nature
of the said Invention, and in what manner the same was to be per-
formed, 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 Andrew Mitchell, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement:-
This Invention consists in employing caissons which are U shaped
horizontally, and one modification thereof comprises a pair connected
together to form what may be termed a bi-valve caisson, which bi-valve
caisson surrounds or encloses the space wherein the pier is to be con-
structed, and when the pier is built up to the water level the parts of
the caisson may be separated or opened, and the whole be withdrawn
and floated away from the pier. The caisson is to be constructed of
wrought iron, and to have a chamber or chambers on its outer side for
floating it and for receiving water or other ballast as required. The
vertical joint surfaces where the two parts meet are to be formed of
wood to receive rubber, and the parts are to be held together by clamps.
and screws during the building of the pier, at which time the water is
of course pumped out of the interior. The lower part of the caisson is
made with single plates so arranged as to readily sink into the mud, and
the continuation of the vertical joints between these plates are formed_
by entering the edges of the plates on one side into angular grooves in,.
the other plates in which grooves rubber is applied. The caisson is

page_text: furnished with shores at the sides to steady it, particularly when the
bottom is uneven. These shores are to be arranged so as to be screwed or
otherwise forced down separately, in order that each may fully bear on
the bottom. In some cases whilst one of the caissons of a pair remain
U shaped, the other may be straight or nearly so. In building con-
tinuous piers or walls sections may be first constructed at short intervals
by means of the bi-valve caisson, and then for filling up each interspace.
two U shaped caissons may be used, one on each side of the line of wall,
and fixed up against the finished parts adjacent to the interspace.
Having thus far particularly described and ascertained the nature of
my said Invention, and incidentally referred to the manner of performing
or putting in practice thereof, in further compliance with the aforesaid.
condition in the said Letters Patent contained I now proceed to par-
ticularly describe and ascertain in what manner the said Invention is
to be performed or carried out in practice, by reference to the Drawings
accompanying these Presents, as follows:-
DESCRIPTION OF THE DRAWINGS.
Fig. 1, section; Fig. 2, plan; Fig. 3, plan of one part of bi-valve
caisson; Fig. 4, plan of both parts together; Fig. 5, section of caissons
built up; Fig. 6, plan; and Fig. 7 section of U shaped caisson.
In the above-mentioned Figures 1. and 2 the bi-valve is represented
as consisting of two cassions 1 and 2 attached to each other at one side
or end d, e, by means of a hinge or other fastening, and at the other e, f,
by means of clamps and screws worked by gearing from the deck a, a,"
a, u. On the outside of the caisson are fixed chambers b, b, b, b, for
receiving ballast of water or other material for giving weight to sink the
same into the ground, and also for floating it, beneath these chambers
are keels i, i, i, i, of single plates. When double keels or double rows
of single plates as i, i, i, i, in section are used they are for strength
subdivided into sections or divisions; these divisions between the double
keels are to have a communication from the deck by what may be
termed man-hole tubes j, through the chambers of the caisson, such
man-hole tubes being provided with doors. The double keels and sub-
divisions are intended to be used on the same principle as diving hells,
so that men may be enabled to get down and remove any obstruction in
.the way of the caisson sinking into the ground, and also for puddling.
When the nature and depth of ground to sink in is ascertained an

page_text: additional depth of keel may, if necessary, be added by screwing or
otherwise fastening on plates to the keels. It is also intended that there
may be a telescope system of plates on the inside at the bottom of the
caisson with rods or bars attached extending up to the deck;
the plates
are jointed into each other vertically working in grooves, and by screws.
or otherwise forced into the ground. In the vertical jointing of the two
caissons wood and rubber are used to make an even and tight joint, the
keel or single plate portions are entered one into the other in angular,
grooves with rubber or other backing.
Another modification of the caisson may be made by building it up. of
sections as a, a, a, Fig. 5, and in half circles, see Fig. 3, having an outer
ring b, b, and an inner ring c, c, and jointing two of these together as
at Fig. 4, at d, d, when they will form a complete circle (though it is
not necessary that the form of the circle should be adopted). The
space e between the outer and inner ring should be made water-tight:
with man-hole doors f, f. These sections a, a, can be added to or.
diminished according to the depth of water to be worked in and one or
more of the bottom sections should be of single thickness for going
into the ground, and in case these lower sections should become too
firmly fixed in the mud or clay so that there is not sufficient floating
power to uplift them, a man can go down through the man-hole doors,
and unfasten the lower sections from the upper. The mode of operation'
of this caisson would be on the same principle as that of the single
caisson now in use.
The U shaped caisson is nearly the same in construction as the bi-
valve and can be used in the same way as at Fig. 6 (plan) by using
a gate piece a, which may be hinged at either end or joint b, b, or
floated into its place in the same manner as caissons in use for dock
gates; the double keel is to be used here as in the bi-valve. When used
for a continuation of building there are two gate pieces c, c, Fig. 7,
hinged or otherwise fastened, working into the caisson at d, d, and hauled
hard up against the building E by chains as used at dock gates; i, pieces
of wood put in between the building and caisson at f to prevent straining
between the pieces of wood i and gate pieces c, c, (with puddled clay g
stamped down,) also having one or more beams from deck to deck
connecting and strengthening the outer parts of caisson. For support
and steadyment of caisson I would use screw pile or common shores k
besides moorings, also I would have beams or shores for strength to

page_text: resist the inward pressure when caissons were large and deep. The
interior space between the inside of the caissons to be built on may be
dredged if the bottom be gravel or hard mud to assist in sinking, also to
clear the space for building; or if soft mud or sand I use a centrifugal
pump laid on the ground with diggers before the suction pipe (and as
presently used for this purpose) to suck and force up the mud and sand,
and also to be used for pumping up the mud and sand between the
double keels as a motive power; for this and other purposes I have a
portable donkey boiler and engine on deck of caisson.
Having now particularly described and ascertained the nature and
object of my Invention, and in what manner the same may be per-
formed or carried out in practice, I hereby declare that I claim, the
herein described "Improvements in Caissons or Apparatus to Facilitate
the Building of Bridge Piers and similar Structures under Water," the
nature and character whereof are set forth in this Specification by the
foregoing descriptive statement.
In witness whereof, I, the said Andrew Mitchell, have hereunto
set my hand and scal, this Twenty-eighth day of May, in the year.
of our Lord One thousand eight hundred and seventy.
Witness,
PETER HUTCHISON,
1, Hamburgh Place.
A. MITCHELL. (L.S.)