Iм- PROVEMENTS IN THE CONSTRUCTION AND WORKING OF CAISSONS, WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO MOVABLE BRIDGES AND THE GATES OF DOCKS AND CANAL LOCKS
Year: 1872

page_text: LETTERS PATENT to David Cunningham, of Dundee, in the County of
Forfar, North Britain, Civil Engineer, for the Invention of “Iм-
PROVEMENTS IN THE CONSTRUCTION AND WORKING OF CAISSONS, WHICH
IMPROVEMENTS ARE ALSO APPLICABLE TO MOVABLE BRIDGES AND THE GATES OF
DOCKS AND CANAL LOCKS."
Sealed the 10th October 1872, and dated the 16th July 1872.
PROVISIONAL SPECIFICATION left by the said David Cunningham
at the Office of the Commissioners of Patents, with his Petition, on
the 16th July 1872.
I, DAVID CUNNINGHAM, of Dundee, in the County of Forfar, North
Britain, Civil Engineer, do hereby declare the nature of the said. In-
vention of "IMPROVEMENTS IN THE CONSTRUCTION AND WORKING OF CAISSONS,
WHICH IMPROVEMENTS ARE ALSO APPLICABLE TO MOVABLE BRIDGES AND THE GATES
OF DOCKS AND CANAL Locks," to be as follows, that is to say:-
This Invention, which relates to improvements in caissons employed for
closing dock entrances, canal locks, and other spaces within which it is
required to confine water, and which improvements may also be applied
)

page_text: to movable bridges, consists in so constructing these caissons, that their
descent and ascent in the water may be effected without the employment
of sluices, valves, or pumps, as hitherto used to admit water to and run
it off from them, in order to alter the amount of ballast, accordingly as
it is desired to sink or raise the caissons.
FL
Under this Invention the caissons are provided with floats at the sides,
which are raised or lowered by screws or other suitable mechanism. By
actuating the screw or other mechanism so as to raise the floats in the.
water the caisson is sunk, and vice versa; by lowering them it is raised,
and by raising the floats clear out of the water they act as weights, by
which the caisson is forced down to its lowest level, thereby keeping
tight the entrance to the dock, canal lock, or other water space, and also
bridging said space.
It is preferred to arrange the floats on both sides of the caisson, as in
such a position. they act as fenders, besides materially contributing to
the strength of the caisson, the screws by which the said floats are
operated being supported in brackets fixed to the caisson at its upper and
lower parts, and it is also preferred to employ in combination with the
floats in cases where the situation is exposed, or where the level of water
is the same on both sides of the caisson, or otherwise, shoulders
projecting from the sides or ends of the caisson, which rest in the side
walls when the caisson or bridge is at its lowest position, by which
means the weight on the caisson. or bridge caused by raising the floats
clear of the water, and also all moving loads on such bridge is sustained,
and the bottom of the caisson or bridge is free to move, and press tightly
on its sill and thereby become water-tight:
'
Towards the lower extremity of the caisson, one or more buoyant
chambers is or are situated, by which the floats are assisted in raising
the caisson when required, and an open space is formed at its upper part
in which the outside water may flow freely, and over which the usual
deck or bridge for traffic is situate.
In lieu of employing floating bodies, in conjunction with the caissons
as herein-before set forth, other bodies which are capable of displacing
water, and whose specific gravity is greater than the water, may be used
for effecting the objects herein-before described, such, for example, as
boxes loaded with pig iron or stones. The caissons, dock or lock gates,
or movable bridges, may also be constructed with one or more tubes

page_text: placed vertically therein, by regulating the atmospheric pressure within
which they may be raised or lowered in the water. In constructing
them according to this arrangement, the tubes are closed at their upper
extremities and open to the water at their lower parts, and they are
made of such area as will, in conjunction with their lengths, enable
at all times a sufficient amount of water to be displaced to give the
necessary buoyancy to float the caisson at the required level.
It is preferred in constructing caissons, dock or lock gates, or movable
bridges, with more than one such tube, to connect the tubes together by
pipes which are also attached to an air pump, and provided with cocks,
through which when it is desired to sink them, the air is allowed to
escape, and when it is desired to raise them in the water, air is forced by
the air pump through the pipes and into the tubes, so as to create an
atmospheric pressure therein sufficient to displace the water which they
contain.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said David Cunningham in the Great Seal Patent
Office on the 15th January 1873.
"
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, DAVID
CUNNINGHAM, of Dundee, in the County of Forfar, North Britain, Civil
Engineer, send greeting.
WHEREAS Her most. Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Sixteenth day of July, in the year of
our Lord One thousand eight hundred and seventy-two, in the 36th
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said David Cunningham, Her special license
that I, the said David Cunningham, my executors, administrators,
and assigns, or such others as I, the said David Cunningham, 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
THE CONSTRUCTION AND WORKING OF CAISSONS, WHICH IMPROVEMENTS ARE ALSO
APPLICABLE TO MOVABLE BRIDGES AND THE GATES OF Docks AND CANAL

page_text: Locks," upon the condition (amongst others) that I, the said David
Cunningham, by an instrument in writing under my hand and seal,
should particularly describe and ascertain the nature of the said
Invention, 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 David Cunningham, 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, reference being had to the accompanying
Drawings, and to the letters and figures marked thereon, that is to
say:-
My said Invention, which relates to improvements in caissons employed
for closing dock entrances, canal locks, and other spaces within which
it is required to confine water, and which improvements may also be
applied to movable bridges, consists in so constructing these caissons
that their descent and ascent in the water may be effected without the
employment of sluices, valves, or pumps, as hitherto used to admit
water to and run it off from them, in order to alter the amount of ballast,
accordingly as it is desired to sink or raise the caissons.
Under this Invention the caissons are provided with floats at the sides,
which are raised or lowered by screws or other suitable mechanism.
By actuating the screws or other mechanism so as to raise the floats in
the water the caisson is sunk, and vice versa; by lowering them it is
raised, and by raising the floats clear out of the water they act as
weights by which the caisson is forced down to its lowest level, thereby
keeping tight the entrance to the dock, canal lock, or other water space,
and also bridging said space.
It is preferred to arrange the floats on both sides of the caisson, as in
such a position they act as fenders besides materially contributing to the
strength of the caisson, the screws by which the said floats are operated
being supported in brackets fixed to the caisson at its upper and lower
parts, and it is also preferred to employ, in combination with the floats in
cases where the situation is exposed, or where the level of water is the
same on both sides of the caisson or otherwise, shoulders projecting from
the sides or ends of the caisson, which rest in the side walls when the

page_text: caisson or bridge is at its lowest position, by which means the weight on
the caisson or bridge caused by raising the floats clear of the water, and
also all moving loads on such bridge is sustained, and the bottom of the
caisson or bridge is free to move and press tightly on its sill and thereby
become water-tight.
Towards the lower extremity of the caisson one or more buoyant
chambers is or are situated by which the floats are assisted in raising the
caisson when required, and an open space is formed at its upper part in
which the outside water may flow freely, and over which the usual deck
or bridge for traffic is situate.
r
In lieu of employing floating bodies in conjunction with the caissons, ..
as herein-before set forth, other bodies which are capable of displacing
water, and whose specific gravity is greater than the water, may be used
for effecting the objects herein-before described, such for example, as
boxes loaded with pig iron, stones, or water. The caissons, dock or lock
gates, or movable bridges, may also be constructed with one or more
tubes placed vertically therein, by regulating the atmospheric pressure
within which they may be raised or lowered in the water.
structing them according to this arrangement, the tubes are closed at
the upper extremities and open to the water at their lower parts, and
they are made of such area as will, in conjunction with their lengths,
enable at all times a sufficient amount of water to be displaced, to give
the necessary buoyancy to float the caisson at the required level.
In con-
It is preferred in constructing caissons, dock or lock gates, or movable
bridges with more than one such tube to connect the tubes together by
pipes, which are also attached to an air pump and provided with cocks
through which, when it is desired to sink them, the air is allowed to
escape, and when it is desired to raise them in the water, air is forced by
the air pump through the pipes and into the tubés, so as to create an
atmospheric pressure therein sufficient to displace the water which they
contain.
And in order that my said Invention may be properly understood, I
now proceed more particularly to set forth the system, mode, or manner
in or under which the same is or may be used or practically carried into
effect, that is to say :-
On the Sheet of Drawings hereunto appended, Figure 1 is a side
clevation of a caisson constructed in accordance with one modification

page_text: of this Invention, and which may be employed for closing dock entrances
or other spaces within which it is desired to confine, or from which
it is desired to exclude water; Figure 2 is a transverse section of the
caisson on the line a, b, Figure 1, whilst Figure 3 is a plan thereof.
As shewn by these Figures the caisson A is provided with floats B
arranged along both of its sides, and which are raised or lowered when
it is desired to sink or raise the caisson by means of screws C passed
through the floats A and supported at their upper and lower ends' in
brackets D and E, respectively fixed to the sides of the caisson, as shown.
On the upper end of each screw C a bevil wheel F is situate, and geared
with a corresponding bevil pinion x situate on the approximate end of a
shaft G extending across the caisson A between corresponding screws at
opposite sides thereof. The bevil wheels F, at one side of the caisson,
are also geared into pinions. I fixed on a shaft I supported in the
brackets D, and on the said shaft I a bevil wheel J is also situate and
geared into a pinion K, as more particularly shewn at Figure 1. When
it is desired to raise or sink the caisson, the pinion K is rotated by means
of a key L passed through an opening in the deck or bridge M, as shewn,
whereby motion is communicated to the shaft I through the wheel J,
and thence by the pinions H to the bevil wheels F on the upper ends of
the screws C situate at the corresponding side of the caisson, an uniform
motion being communicated to the screws at the opposite side of the
caisson by the pinions x and shaft G. By this means the floats B, on
being uniformly raised, cause the caisson A to sink in the water, and by
lowering the floats the caisson is raised, or by sinking the said floats
below their natural level of flotation greater buoyancy is imparted to the
caisson.
2
Towards the lower part of the caisson A buoyant chambers N are
situate, as shewn at Figure 2, by which the floats B are assisted in
raising the caisson when required. The upper buoyant chamber N
is situated sufficiently low to enable the caisson to be raised when the
water is at the lowest level at which it is intended to open the entrance
to the dock or other water space, and between the buoyant chambers N
and the deck or bridge M an open space is formed in the caisson, as
shewn, in which the outside water may flow freely.
An amount of ballast may be placed in the lower chambers N¹ to
steady the caisson if required.

page_text: A passage P is constructed in the caisson communicating between
the deck or bridge and the upper buoyant chamber N, in order to afford
facility of access to the interior of the said chamber, from whence access
is obtained to the other chambers N and N¹ through doorways R situate
in the bottom of each, as shewn at Figure 2.
In employing the caisson herein-before described, it is preferred to
use in combination with the floats B shoulders projecting from the
ends of the caisson, as shewn at S, Figures 1 and 3, which rest in the
side walls when the caisson is at its lowest position, by which means
the weight on the caisson caused by raising the floats clear of the water,.
and also all moving loads on the deck or bridge are sustained, and the
bottom of the caisson is free to move and press tightly on its sill, and
thereby become water-tight.
In lieu of arranging the floats B (which are more than sufficient in
weight and displacement to compensate for the difference of displace-
ment caused by the caisson between its highest and lowest levels)
on both sides of the caisson, as herein-before described and shewn on
the Drawings, the said 'floats may be placed at one side only of the
caisson; but it is preferred to arrange the floats as illustrated, as in
such a position they act as fenders besides materially contributing to
the strength of the caisson; and in lieu of employing floating bodies
in conjunction with the caissons, other bodies which are capable of
displacing water, and whose specific gravity is greater than the water,
may be used for effecting the objects herein-before described, such for
example as boxes loaded with pig iron, stones, or water.
Under another modification of my said Invention illustrated in sido
elevation at Figure, 5, in transverse section on the line c, d, Figure 5,
at Figure 6, and in plan at Figure 7, the caisson A, in lieu of being
provided with floats, is constructed with pneumatic tubes B placed
vertically at each end thereof, as shewn more particularly at Figure 1,
and by regulating the atmospheric pressure within these tubes the
caisson is raised or sunk in the water as desired.
In constructing caissons according to this arrangement the tubes B
are employed in conjunction with buoyant chambers C similar to those
herein-before described, and which are situate towards the lower part
of the caisson, as shewn at Figure 6, and an amount of ballast may be
placed in the lower buoyant chambers C' in order to steady the caisson.

page_text: An open space in which the outside water may flow freely is situate
between the buoyant chambers and the usual deck or bridge for traffic.
The tubes B are closed at their upper extremities and open to the water
at their lower parts, and they are made of such area and length as will
at all times enable a sufficient amount of water to be displaced from
the interiors of the tubes, to give in conjunction with the buoyant
chambers C the necessary buoyancy to float the caisson at the level
required, or the chambers C may be made of sufficient buoyancy to
float the caisson; in which case the sinking of the caisson is effected
by withdrawing or partially exhausting the air from the tubes B, and
'thereby allowing the water to rise therein. Pipes F, communicating
with compressed air chambers G situate at each side of the man-hole
or passage H, are arranged in connection with the upper parts of the
tubes B, as shewn, and when it is desired to raise the caisson in the
water, a pipe communicating with an air pump or pumps conveniently
situated at a position removed from the caisson, is coupled to the pipe I
communicating with the air chambers or receivers G, by which means
air is forced into the said chambers and from thence passes through the
pipes F and three-way cocks or valves J into the tubes B, thereby
displacing and forcing the water outwards from the bottoms of the said
tubes and raising the caisson A to the level required.
As shewn on the Drawings the three-way cocks or valves J are
arranged to be opened and shut by hand wheels actuated through
suitable openings in the deck or bridge K, but the said cocks or valves J
may be otherwise actuated, as for example-they may be arranged to be
opened and shut in unison and by the same apparatus; and in lieu of
arranging the air chambers or receivers G in such a manner that the air
when compressed thereinto is immediately led to the tubes B, the said
chambers may by providing them with additional valves or cocks in the
pipe I be made to act as reservoirs for storage of compressed air, which
may on opening the valves or cocks J be allowed to enter the tubes B,
as herein-before set forth. An air pump or pumps may be situate on
the caisson itself, and connected to the chambers or receivers G, or
direct to the pipes F.
When it is desired to sink the caisson A. the three-way cocks or
valves J are turned so as to effect communication between the atmo-
sphere and the interiors of the tubes B, by which means the compressed
air is allowed to escape out of the said tubes when the water again rises-

page_text: .
at the lower parts thereof, and the caisson is thereby sunk. Separate
pipes or passages, provided with stop cocks or valves may be arranged
in connection with the tubes B for the escape of the compressed air
therefrom when it is desired to sink the caisson in. lieu of employing
three-way cocks or valves for that purpose, as herein-before described
and shewn on the Drawings.
The caisson, shewn at Figures 5, 6, and 7, is provided with shoulders x,
and when the caisson is in position for closing the entrance to the dock
or other water space, or when it occupies a similar position to that indi-
cated in dotted lines on the diagram plan, Figure 4 (at which time the
entrance to the dock or other water space is open), these shoulders ≈ rest
in the side walls, by which means the weight of the caisson may be
sustained, and the caisson when the entrance to the dock or other water
space is closed thereby is free to move and press tightly on its sill, and
thereby become water-tight.
Figure 8 is a diagram longitudinal section of a modified arrangement
of the caisson now last described, and in this instance the tubes A are
formed with air-tight compartments B at their upper ends, as shewn,
into which air is compressed by an air pump or pumps, and stored
therein until it is desired to raise the caisson in the water, at which
time cocks or valves situate in pipes or passages C communicating
between the air reservoirs B and the lower parts of the tubes A are
opened, thereby allowing the air to pass into the said lower parts of the
tubes A, whereby an atmospheric pressure is created therein sufficient
to displace and force out the water contained in the tubes.
Under another modification illustrated by the diagram, Figure 9, the
air tubes may be constructed detached from the body of the caisson in
lieu of forming part thereof, as hercin-before described and shewn at.
Figures 5, 6, and 7. Under this arrangement, when the caisson is not
immediately to be raised or lowered for opening or closing the entrance
to the dock or other water space, the air tubes are allowed to float in the
water, and are kept in close proximity to the caisson by suitable
guides A situate on the caisson or adjacent thereto, and when the caisson
is about to be raised the tubes are secured in position by set screws or
other suitable means, and the caisson raised by pumping or forcing air
into the tubes so secured, and again sunk by allowing the compressed
air to escape therefrom.

page_text: It is to be here understood that in lieu of constructing the caisson
with two pneumatic tubes in conjunction with the buoyant chambers, as
herein-before described, that the caisson may be constructed with a
greater number of such tubes, or it may be constructed with one such
tube only; and it is further to be understood that the arrangement
now last set forth, and also the arrangements of tubes illustrated at
Figures 5, 6, and 7, at Figure 8, and at Figure 9, and the arrangement
of floats illustrated at Figures 1, 2, and 3 are, whilst applicable to
caissons, cqually applicable to movable bridges, and the gates of docks
and canal locks.
Figure 10 is a side elevation, and Figure 11, a transverse section on
the line e, f, Figure 10, of a movable, bridge constructed in accordance
with the modification of the tube arrangement last set forth. As shewn
by these Figures the bridge is formed with a buoyant chamber A at its
lower part, and which is so situate as to impart the necessary buoyancy
to the bridge whilst the water is at its lowest level. The air tube B is
placed at one end of the bridge, and is provided at its upper part with a
three-way cock C and pipe D, which latter communicates with a com-
pressed air receiver E, into which air is compressed by a pump or pumps
removed from the bridge when it is desired to raise the bridge, or the
pipe D may be coupled direct to an air pump placed on the bridge
itself.
When it is desired to open the space closed by the bridge shewn at
Figures 10 and 11, air is compressed into the tube B, so as to create an
atmospheric pressure therein sufficient to displace and force out the
water. By this means the bridge is raised at the end whereat the
tube B is situate, and is thereafter turned back, so as to leave the space
clear on a hinge or swivel apparatus situate at its opposite end. Suffi-
cient play or elongation is given to the lower hinge of the bridge or of
the caisson (in instances where such caissons are anchored to the side
wall, and provided with the arrangement of air tube last set forth) to
allow of the bridge or caisson being raised as above mentioned with
facility.
The different arrangements of caissons herein-before described and
shewn on the Sheet of Drawings hereunto appended, may, whilst
permanently steadied by ballast placed in the lower chambers thereof be
1.

page_text: Having now described and particularly ascertained the nature of my
said Invention, and several systems or modes in or under which the same
is or may be used or carried out in practice, I would observe in con-
clusion that I do not claim constructing caissons, movable bridges, or
the gates of docks or canal locks with shoulders, as herein-before
described and shewn on the Drawings; but what-I do 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,--
First. Constructing and arranging caissons, movable bridges, and the
gates of docks or canal locks with buoyant chambers situate at or
towards their lower parts, and with floats or other displacing bodies
arranged at one or both sides, as herein-before described and shown at
Figures 1, 2, and 3 of the Drawings.
Second. Arranging and constructing caissons, movable bridges, and
the gates of docks or canal locks with one or more pneumatic tubes in
combination with buoyant chambers by regulating the atmospheric
pressure, within which tubes the caisson, bridge, or gate is raised or
sunk, as herein-before described and shewn at Figures 5, 6, and 7, and
at Figures 10 and 11 of the appended Drawings..
Third. The employment of the arrangement of pneumatic tubes
illustrated in diagram at Figure 8 of the Drawings in conjunction with
caissons, movable bridges, or the gates of docks or canal locks, as and
for the purpose herein-before described.
Fourth. Arranging the pneumatic tubes in the manner herein-before
described and shewn in diagram at Figure 9.
In witness whereof, I, the said David Cunningham, have here-
unto set my hand and seal, this Tenth day of January One
thousand eight hundred and seventy-three.
DAVID CUNNINGHAM. (L.S.)