Improvements in Coffer Dams or Sectional Docks for Inspecting and Repairing the Submerged Portions of Ships and like. Structures.
Year: 1888

page_text: Date of Application, 20th Mar., 1888
Complete Specification Left, 20th Dec., 1888-Accepted, 20th June. 1889
Improvements in Coffer Dams or Sectional Docks for Inspecting and
Repairing the Submerged Portions of Ships and like. Structures.
I, CHARLES JAMES Fox, of Hemingford Terrace, Birkenhead, in the County of
Chester, Master Mariner do hereby declare the nature of the said invention to he as
follows:-
The type of apparatus to which this Invention relates has for its object to render it
possible to gain access to inspect and repair those portions of ships and like structures,
which are under ordinary conditions submerged, that is lie below the free surface
of the water in which they float and while the ship, or other like structure is
afloat.
A coffer dam, or sectional dock with my improvements applied thereto consists as
follows: For convenience of description the vessel of the dock may be said to
consist principally of two portions, these two portions lying one within the main
gates hereinafter described and the other without the main gates, but between such
gates and auxiliary gates hereinafter described. This portion I call the foregate, and
the other portion the body. Both these portions are cellular construction and I
prefer to divide them horizontally and perpendicularly by one, or more watertight
bulkheads. The upper compartments so formed may be used to serve either as air
chambers or water chambers as and when so desired. For instance when the dam is
applied to a ship, the compartments which will be above the water level might be
supplied with water. By this means the upward pressure of the damn and its tendency
to lift is diminished. These compartments when air filled, or some of them, might
also serve as means of preventing the dam sinking should the other parts become filled
with water at any time.
The main gates of the dock consist of two series of arms hinged one on each side of
the dam and free to move about their hinges in the horizontal plane, the free ends of
which arms can be brought to bear when applied against the side of the ship. These
arms will be hereinafter again reicrred to.
The second, or supplementary gates above mentioned are provided to the front of the
foregate portion and are used to keep the dock dry inside, when it is not in use. These
gates are preferably in the form of low half dock gates hinged to a transverse bulkhead.
When the dock is about to be applied to a ship the supplementary gates are opened,
but when it is withdrawn the gates are closed. The water within the dock can then
be pumped out, and it can then be easily towed. These features merely demonstrate
some of the advantages attending the use of these front gates.
The dock is as above stated of cellular formation, but beyond this I prefer to
construct it with rounded, or curvilinear bottom, or bilges and in the case of a
"stern," or "stem
dock I also construct its closed end of rounded formation. In
the compartments of this end, engines, boilers and pumping apparatus are placed.
I connect the pumping apparatus with the different tanks of the dock by pipes
suitably disposed and on this system of pipes I also provide cocks, or valves by the
operation of which the different tanks, or compartments can be emptied, or filled as
desired and by which the raising, sinking and balancing of the dock can be effected
and fully controlled. I may further provide valves in the diaphragms by which
communication between the different compartments may be made. The pumping
apparatus I may also use for pumping out the dock when it is applied to a vessel.
also provide other sluice valves, or cocks by which communication through the shell

page_text: of the dock and between the outside and its inside can be made and used for any
purposes.
Through the compartments at the closed end of the dock is provided an aperture
and way for gaining access, or egress to, or from the lower portion of the dock
and so that articles can be freely raised, or lowered from, or into the dock the
raising, or lowering apparatus being preferably suspended, or rigged from, or upon
the stem, or stern of the vessel to which the dock applied. In this way I may
provide suitable stairs, steps, or a ladder for communicating between the bottom and
the deck of the dock.
The hinged arns above mentioned may be operated, controlled and made practically.
water tight when applied to a vessel by the following means. To the end and outside
of the arms I may provide other hinged, or secondary arms one or more of which
but preferably a number will be hinged to each of the main arms. Thus one end of
these secondary arms would be supported by the main arms and the other by the
vessel. In this way it is possible to have the areas of the apertures that necessarily
occur between the outer part of the free ends of the arms and the ships surface far
less than those that would exist if the main arms only were used 1 can thereby use
canvas, or other textile, or pliable material comparatively thin, to cover these
apertures over the secondary arins to effect a complete watertight joint at the point. of
contact of the secondary arms and the ships surface. This pliable material may be
applied after the arms are in position, or it may be attached to the arms in the form
of a flap, or in any convenient manner.
The main arms if used alone, or in combination with secondary arms may be
provided with pliable material, such as canvas, or rubber, over the whole in one piece,
or it may be affixed to the arms in pieces and lie over the seams of the arms in flaps ;
and it may be attached either at one, or both edges; but if the latter mode is adopted
the material must be "balooned " so as to allow free and independent movement of
the arms.
If it may be found necessary, or desirable I may fix to the secondary arms
a flexible piece of brush, or equivalent wood, rubber or equivalent material, which
further aids to make a joint and which also serves to support a sheet of canvas which
may be laid, or spread over the whole and make the joint tight.
In the cases where I apply a pad of flexible material to prevent water passing
between the ends of the arms and the ships surface, I place such pad outside the
tips of the arms and make the pressure of the water so serve as the means of keeping
it in position. This pad may be made of canvas, canvas and rope, rubber, or any
combination of these materials, or their equivalent, that is materials that are strong
enough to withstand the pressure of water and at the same time are sufficiently flexible,
or pliable to serve the purpose for which they are intended.
To relieve the arms from a tendency to lift and cant I weight them. This may
be suitably done by applying a sheet, or plate of iron either at the bottom, top sides
or edges or in the middle of each arm, by which means the above end would be secured,
and the arms would also be strengthened and liability to warp diminished. The same
effect may be produced by providing a stud on cach arm and causing it to work in a
corresponding groove in the arm next above, or below it or by equivalent devices.
The lower arm in this case would be provided with a similar device to hold it to the
floor of the dock. These devices may be made to serve as means for preventing the
arins from being moved beyond the proper amount on one another. The end however,
I may also attain by connecting the several arms together by chains, ropes, or bars
of the required length and so limiting the movement of any two arms upon one
another.
As a means for preventing the dock from canting at any time I may secure, or
moor a Hoating pontoon on either side of it. The effect of this would be that when
the dock commenced to cant the additional weight of the pontoon on one side would
be brought to bear on that side of the dock and further motion in the direction
of the cant prevented, and the weight in the opposite side would be relieved and
diminished.

page_text: The arms may be of single piece, or built up of planks, or a compound of wood
and metal.
Dated this 10th CM 1 1000
COMPLETE SPECIFICATION.
Improvements in Coffer Dams or Sectional Docks for Inspecting and
Repairing the Submerged Portions of Ships and like Structures.
I CHARLES JAMES Fox of Hemingford Terrace, Birkenhend. in the County of
Chester Master Mariner, 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 :—
The type of apparatus to which this Invention relates, has for its object to render it
possible to displace water from, gain access to, inspect and repair those proportions
of ships and like structures which are under ordinary conditions submerged, that is,
lie below the free surface of the water in which they Hoat, and while the ship or other
like structure is afloat.
A coffer dam, or sectional dock with my Improvements applied thereto consists as
follows: For convenience of description the vessel of the dock may be said to
consist principally of two portions. these two portions lying, one within the main -
gates hereinafter described, and the other without the main gates, but between such
gates, and auxiliary gates hereinafter described. This portion I call the fore-gate and
the other portion the body. Both these portions may be of cellular construction and
I prefer to divide them horizontally and perpendicularly by one, or more water tight
bulkheads. The compartments so formed may be used to serve either as air chambers,
or water chambers or tanks, as and when so desired. For instance, when the dam is
applied to a ship the compartments which will be above the water level might be
supplied with water. By this means the upward pressure of the dam and its tendency
to lift would be diminished. These compartments when air filled, or some of them.
might also serve as a means of preventing the dam sinking should the other parts
become filled with water at any time, and are useful also to regulate its draft.
The main gates of the dock consist of series of arms hinged on the side or
bottom of the dam, and free to move about their hinges in the horizontal plane or
otherwise, the free ends of which arms can be brought to bear when applied against
the sides and bottom of the ship. These arms will be hereinafter again referred to.
The second or supplementary gate or gates above mentioned are provided to the
front of the foregate portion and are used to keep the deck dry inside, when
it is not in operation upon a ship and may be fitted like ordinary dock gates,
either permanently hinged, or removable, as are caisson gates; but in the latter
case it is not necessary under all conditions that they would possess floatative power
as in some cases where they would be very small they could be easily handled by other
means. When the dock is about to be applied to a ship the supplementary gates are
opened, and when it is withdrawn they can be closed. The dock can then be pumped.
out and dried and it can then be easily towed. These features merely demonstrate
some of the advantages attending the use of these front gates.
::
In
The dock is. as above stated, of cellular formation, but beyond this I prefer to
construct it with rounded, or curvilinear bottom, or bilges, and in the case of a
stern ог "stem" dock, I also construct its closed end of rounded formation.
the compartments of this end, engines, boilers and pumping apparatus are placed.
I connect the pumping apparatus with the different tanks of the dock by pipes
suitably disposed, and on this system of pipes also provide cocks, or valves by the
operation of which the different tanks, or compartments can be emptied, or filled
as desired and by which the raising sinking, and balancing of the dock can be
effected and fully controlled. I may further provide valves in the diaphragms by,
which communication between the different compartiments may be made!" The

page_text: pumping apparatus I may also use for pumping out the dock when it is applied
to a vessel. I also provide other sluice valves or cocks by which communication
through the shell of the dock and between the outside and its inside can be made and
used for flooding or other purposes.
Through the compartments, at the end of the dock, is provided an aperture and way
for gaining access, or egress to, or from the lower portion of the dock, and so that
articles can be easily raised, or lowered from, or into the dock; the raising, or lowering
tackle being preferably suspended from, the stein, or stern of the vessel to which
the dock is applied. In this way I may provide suitable stairs, steps or a ladder for
communicating between the bottom and the deck of the dock.
"
The hinged arms above mentioned may be operated, controlled, and made practically
watertight when applied to a vessel by the following means. To the end and outside
of the arms I may provide other hinged or secondary arms, two or more of which
will be hinged to each of the main arms. Thus one end of these secondary arms
would be supported by the main arms and the other by the vessel. In this way it is
possible to have the areas of the apertures, that necessarily occur between the outer
part of the free ends of the arms, and the ships surface, much less than those that
would exist if the main arms only were used, I can thereby use canvas, or other
textile, or pliable material comparatively thin to cover these apertures over the
secondary arms to effect a complete water-tight joint at the point of contact of
the secondary arms and the ships surface. This pliable material may be applied after
the arms are in position, or it may be attached to the arms in the form of a flap, in
any convenient manner.
The main arms if used alone, or in combination with secondary arms may be
provided with pliable material such as canvas or rubber over the whole in one piece,
or it may be affixed to the arms in pieces, and lie over the seats of the arms in flaps,
and it may be attached either at one or both edges, but if the latter mode is adopted
the material must, be applied in "bellows" form, so as to allow free and indepen-
dent movement of the arms. If it be found necessary or desirable, I may fix
to the secondary arms a flexible piece of brush, or equivalent wood, rubber or
equivalent material which further aids to make a joint and which also serves as a
bridge to carry strips or a sheet of canvas which may be applied in bellows" form
or spread over and beyond them to the ship and makes the whole water-tight.
canvas may be doubled or "thrumed if necessary.
This
When necessary to relieve the arms from a tendency to lift and separate, I weight
them. This may be suitably done by applying a sheet or plate of iron either at the
bottom, top, sides or edges, or in the middle of each arm, by which means the above
end would be secured, and the arms would also be strengthened, and liability to warp
diminished. The same effect may be produced by providing a stud on each arm and
causing it to work in a corresponding groove in the arm next above, or below it, or
by equivalent devices. The lower arm in this case would be provided with a similar
device to hold it to the floor of the dock. These devices may be made to serve
as means for preventing the arms from being moved beyond the proper amount
on one another. This end however, I may also obtain by connecting the several arms
together by chains, ropes or bars of the required length and so limiting the movement
of any two arms upon another.
As a means for preventing the dock from canting at any time I may secure or
moor a floating pontoon on either side of it. The effect of this would be that
when the dock commenced to cant the additional weight of the pontoon on onc
side would be brought to bear on that side of the dock and further motion in the
direction of the cant prevented, and the weight in the opposite side would be
relieved and diminished.
The arms may be of a single piece, or built up of planks, or a compound of
wood and metal.
In Figures 1, 2 and 3 is shown, in sectional elevation, plan, and half section,
and half outside elevation respectively, a coffer dam according to this Invention
built of metal. The construction is that precisely as specified in the earlier portion

page_text: of this specification, wherein it describes a coffer dam having a foregate portion,
rounded end and bilges, etcetera. With reference to the views. A are the main
gates of the dam hinged at A¹ and adapted to move about their hinges in the
horizontal plane; B are the half dock gates hinged at B₁ to the transverse bulk
heads B2 C designates the body of the dock, composed of inner and outer walls c¹³,
braced together by struts and ties ³, and provided with a longitudinal bulk head c
and vertical bulk heads ; D designates the foregate portion, composed also of
inner and outer walls dd, braced together by suitable struts, and separated from
the body C by vertical bulk-heads H is the sill of the doors A and E is the
embayment leading from the deck of the dock of the bottom, and in which a ladder
or stairs may be placed to get to and from the bottom of the dock and for other
purposes hereinafter described.
It will be seen that the bulk heads cand e separate the double shell of the body C
of the dock into a number of chambers or tanks isolated from each other, namely,
there will be in the first place, an upper chamber and a lower one, formed by the
bulk head, and those chambers will again be each divided into three. It will thus
be obvious, if these chambers be provided with pipes connected to, or adapted to be
connected to, a pump or pumps, any or all of them may be emptied at pleasure; and
also if sluice valves, such as f, be placed on the skin of these chambers by opening
the valves the chambers may be filled. By the opening, closing and regulating of the
valves and pumps, assuming the foregate portion to be also provided with same, any
required regulation or control of the dam, when applying it to or taking it from under
a vessel or at other times, as to making it, raising it, canting it endwise or to one or
other side, and the like, may be effected. In the drawing a pump F and boiler Fis
illustrated, and shown placed in the aft part of the upper stern chamber; a similar
pumping apparatus may be placed in the other side of this chamber, and both used to
empty the various tanks as required, suitable valves being placed on the pipes
communicating with the various chambers.
It will be observed the stern of the dock is rounded, as are also the bilges, and that
the stern chambers are of greater breadth than the side ones. These features of
construction provide easy towage of the dock, and a larger space for machinery and
other tackle required to work the dock.
The bottom of the dock is of double or cellular construction and forms part of the
lower side chambers, except at the centre where they terminate and a well G is
formed, in which the blocks or chocks, which come against the keel of the vessel
being docked, are placed as shown in Figure 2.
The purposes of the front or foregate half gates B are fully set forth in the early
portion of this specification already referred to, and need therefore no further
description.
"
In the plan in Figure 2 the secondary arms designated a are shown. These arms
consist of a number of bars of smaller depth than the main arms A, and are hinged
to the main arms, by suitable hinges, in the manner more clearly shown in Figure 3*.
Here it will be seen the arms are not hinged directly to the extremities of the main
arms, but some considerable distance from them. By this mode of fixing the auxiliary
or secondary arms, they will be prevented from swaying inwards and the continuity
of the line formed by their ends against the ship less disturbed by the irregularities of
the greater arms, thereby when the dock is being applied to a vessel they would
always be in the desired position.
An equivalent provision to the secondary arms a is illustrated in plan in Figure 4.
In this instance I secure in any suitable way, brushwood, cane, or like or equivalent
pliable material, to the arms A, by plates e arranged above and below and fixed to the
upper and lower edges of the arms. As previously stated, the function, of all the
secondary arms, or their equivalents, hereinbefore or hereinafter described, is to
provide a means whereby the joint of the arms with the ships skin shall be as close
and good as possible, and requiring little padding, of the nature herein referred to,
or, canvas or other sheets, to render it practically water tight; and they have a
further object, namely, to prevent the pressure of water upon the canvas or padding

page_text: being concentrated upon large surfaces, or in other words, to afford support to the
padding or canvas at a large number of points, so as to distribute, as much as possible,
the pressure upon them.
Another arrangement illustrated in Figures 5 and 6, by which a number of
secondary arms are secured to each of the main arms A, consists of a foot piece a',
hinged at a and having a plurality of arms a hinged at the end thereof. In operation
the sole of the foot awhich would be preferably rounded transversely upon its
inner surface would, when applied to the ships side, rest thereon and the ends of the
arms a would make contact also with the skin of the ship (designated x), and would
form the joint and support pad, canvas or other material which would be spread over
the outside.
In Figures 7 74 and 7 are shown the means by which the arms may be prevented
from being canted upwards, when made of wood, and lighter than the water. In the
arrangement in Figures 7 and 74, the arm A is provided in the one case with the
upper and lower metal plates a³, whilst in the other, the plate a³ is sandwiched
between two wood portions. In either case the wood and metal forming the composite
arms would be held together by suitable bolts or rivets. In Figure 78 the lowest
arm of the dock gate is shown; it is provided with a stud at in its lower side, and
this stud is arranged to slide in a groove or channel a³, provided in or upon the sill H
of the dock.
According to another arrangement shown in Figure 7° to confine the passage of
the lower arm always in the same plane I carry a rod or stay at from a point as nearly
as possible to its axis and some distance above the arm to a point some distance along
the arm, and hinge it at both ends. This stay is inside of the gate as the arms in
nearly all cases curve outwards from the lower arm; but as it may be desirable to use
a similar stay on the other arms which occasionally curve inwards I lengthen the neck
of the eyebolt or build a bulge on the arm to secure the hinged end of the stay to so
as to allow the arm next above some room to travel inwards.
To prevent the neighbouring arms separating and to ensure their moving in parallel
planes I secure a stud to one arm working in a channel in the neighbouring arm
after the manner set forth with reference to Figure 7B and the edges of which channel
loosely grasp the stud so as to allow it to travel freely along the channel but prevent
its withdrawal at right angles. The channel being closed at its ends also serves to
prevent the arms being parted transversely more than required.
In the case of the lower arm the stud a works in an extended groove in the sill or
platform as shown in Figure 7B; or vice versa, if the button be on the sill, it would
be extended into a I shaped iron bar or rod working through a corresponding groove
in the arm.
To facilitate the passage of the arms transversely over each other I may introduce
and fix Roller or Ball bearings between them and arranged in any known suitable
way.
In addition to or in lieu of using plates of iron between the planks of the arms, or
plating them on one or more sides or edges, which serve as ballast for them, a piece
of cable may be secured to the top of the gate and be allowed to hang down on the
inside so that it will rest on the edges of each arm as they curve outwards from the
bottom.
I may also use a piece of chain, rope, or wire, siezed to an eye bolt near the free
end of each arm to regulate the extent to which they may be opened transversely, or
I pass a bar, wire, rope, or chain through these eye bolts for the same purpose. By
this means I am enabled to pull in more than one arm at a time with one rope
from the after end of the dam.
In Figures 8, 9, 10, and 11 is shown a dock according to my Invention con-
structed of timber, and having a slightly modified form of main gates. In this
instance the inner skin c¹ of the lower portion of the side chambers, or tanks of
the dock, below the horizontal diaphragm care inclined, extending inwards as
shown and these triangular portions of the chambers are carried forward in front
of the gate post A², and are rounded off as shown in plan in Figure 11; the

page_text: gate post A is held by a strap A* at the top, and is mounted in a footstep at Aº,
set in the apex of the said rounded end of the chamber.
In this instance the gates are made of a main and secondary part as above
described, but instead of the main portion consisting of a number of hinged bars or
arms, it is made of a plain solid door A, of triangular form, having secondary arms a
hinged outside the door A and in a line extending from the top of the gate post,
approximately, to the toe Aº.
In Figure 8 the arms a are arranged horizontally, and in sets, a number being
hinged on one spindle a²; whilst in Figure 9, the preferable form, all the arms are
arranged at an inclination and are hinged on a common spindle a²; the top portion
of the gate a in this latter case is solid. Further smaller arms or pliable material
may, if desired, be provided on the ends of the arms a, in the manner of the arms a
in Figures 34, 4, 5, and 6.
Another arrangement of arms is illustrated in Figures 12 and 13 in plan and
perspectively, respectively. In this instance the arms are hinged to the sill of the
dock and are also arranged in an inclined manner, and hinged in the manner set
forth with reference to Figures 8 and 9, but the inclination exists with reference to
the longitudinal centre line of the dock, and the arms are arranged to move about
their pivots or hinges in the vertical plane. It will be seen that the arms vary in
length, those being longest near the ends of the. body (, and shortest near the
centre of the sill H where. the two sets of arms meet this graduation of length
may be carried out in any way that may be desired, and according to the purpose
for which the dock may be intended. It will be observed, in this case, the ends of
the side tanks or chambers of the body C are arranged at right angles to the
angular direction of the hinges of the arms A, when viewed from the top and
looking down. The upper ends of the arms A may be wider than at the hinge in
order to allow of them being opened to a greater extent than if narrow as shown
in the Figures.
This arrangement of arms is particularly suitable for coffer dams or sectional docks,
baving doors arranged at each end, and for being applied to ships having "flat floors"
and straight sides"; but at the same time, it may be applied to those docks having
doors, only at one end.
"
As a modification to the manner of arranging the foregates B they may be hinged
horizontally to the front edge or at any other convenient point of the sill of the dock
main gates; in which case they will of course move about their hinge or axis in the
vertical plane.
To meet the difficulty of constructing a coffer dain or dock adapted to be placed on
a deep drafted and narrow beamed ship and also on a light drafted and broad beamed
ship without greatly increasing its side and lifting power, I arrange for a series of tanks
or pontoons such as L in Figure 14 being hinged or otherwise secured to the upper edge
of the main construction so that they can be turned up or down on the outside as
desired; or they may be made to rise and fall perpendicularly by Tirons on the tanks
sliding in grooves on the dam.
l
To operate the pontoons L, I secure chains or ropes to them, and lead these down
outside through sheaves in the shell of the dock; and up through tanked spaces or
tubes in the upper portion of the main dan. These chains or ropes can be operated
by tackle or gipsy winches, but preferably I wind them on a strong iron bar sup
ported on bearings and provided with sockets in which handspikes can be shipped
to lever it round and also with pawl wheels, and pawls to lock the gear. To lengthen
the gates I ship a tube on the end of the bar on which the lower gate arms are hinged
the head of which is purposely lengthened a few inches and thus carry the hinge bar
to the required height, on this tube the extra arms required are placed. The gate
post is lengthened by an extra piece secured to the end of a pontoon which is also
provided with a clamp to secure the upper end of the tube.
It will be apparent that when the tanks are raised and the main dam lowered with
the extra gates and fixtures arranged, a deep narrow dam is formed, and when the

page_text: tanks are drawn down a comparatively broad shallow dam is secured, adapted to work
under the overhang of the stern of a low ship without coming in contact therewith.
::
It may here be conveniently remarked that although a foregate" portion to all
forms of docks may be employed with advantage, especially for the purposes herein set
forth, yet its use under any circumstances may not be absolutely necessary or even
desirable; and therefore I would have it understood that the arrangements and parts
of the docks herein described, may be employed independently of the "foregate
portion. An example of this is illustrated in Figures 8, 9, 10 and 11 in which no
foregate portion is provided, merely a sill H being provided and constituting
a prolongation of the bottom of the dock.
"
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
1. A sectional dock or coffer dam, having at one end hinged gates, the other end
and sides being composed of chambers, and the stern being formed substantially as
set forth.
2. A sectional dock or coffer dam comprising two portions, one being the body,
within which the portion of the ship to be inspected or operated upon comes, when
docked, and the other or others a portion or portions in front of the main gates of the
body, and provided with smaller gates for the purposes set forth.
3. A sectional dock or coffer dam of the kind herein described provided with inner
and outer skins, the space between said skins being divided by bulk heads into a
plurality of chambers or tanks, substantially as and for the purposes set forth.
4. In a sectional dock or coffer dam of the kind herein described, the body of which
is constructed of an inner and outer skin as described, a passage or embayment (such
as E), provided in the stern thereof, for the purposes set forth.
5. In a coffer dam or sectional dock of the kind herein described, a portion con-
structed in front of the main gates thereof and provided with secondary gates or
doors substantially as and for the purposes set forth.
6. In a coffer dam or sectional dock of the type herein described the combination of
a body within which the portion of the ship to be inspected or operated upon causes
when docked, hinged gates adapted to bear upon the skin of the ship for the purposes
described, and a secondary gate or gates arranged outside aforesaid, gates, for the
purposes set forth.
7. In a coffer dam or sectional dock of the kind herein described, gates consisting
of a plurality of arms, provided with a plurality of secondary arms, hinged to the
aforesaid arms, and adapted to operate substantially as set forth.
8. In a coffer dam or sectional dock of the kind herein described, gates consisting
of a plurality of arms provided with brushwood, cane or equivalent material, and
adapted to operate substantially as set forth.
9. A gate for coffer dams or sectional docks of the kind herein described composed
of, or comprising a rigid or solid hinged portion, and a plurality of arms hinged
thereon, and adapted to operate substantially as set forth.
10. A gate for coffer dams or sectional docks of the kind herein specified composed
of or comprising a rigid or solid hinged portion, and a plurality of arms hinged
thereon, having their hinges arranged at an inclination, and adapted to operate
substantially as set forth.
11. A coffer dam or sectional dock of the kind herein described having its gates
hinged horizontally, and arranged at an inclination to the direction of its length,
substantially in the manner set forth with reference to Figures 12 and 13.
12. In a coffer dam or sectional dock of the kind herein described, wherein its gates
are hinged horizontally and arranged at an inclination to the direction of its length
as specified in the next preceeding claim, constructing the ends of the sides of said
dam at right angles to the axis of the arms, substantially as set forth.
13. A coffer dam or sectional dock having chambers or tanks extended in front of
the main gate thereof, substantially as set forth.

page_text: 14. A coffer dam or sectional dock having lower chambers or tanks extended in front
of the main gates, the lower hinges of such gates being arranged at the upper part of
said extended chambers or tanks, substantially in the manner set forth with reference
to Figures 8, 9, 10 and 11.
15. The construction of main and secondary arms or portions A, a, of the dock gate,
of the kind herein described, substantially as set forth with reference to Figures 34, 4,
and 5 and 6, respectively, of the drawings.
16. The means substantially herein described by which the limit of movement of
the arms with respect to each other, of a coffer dam or sectional dock gates of the
kind herein described is obtained.
17. The means substantially herein described which the arms when formed mostly
of wood of a coffer dam or sectional dock gato of the kind herein described are
prevented from being canted when submerged.
18. A dock gate composed of a plurality of arms A, said arms being provided
with or composed of wood and metal substantially as set forth for the purposes specified.
19. In a coffer dam or sectional dock, of the kind herein described, the closed
chamber or pontoons L, hinged on the body of the dam or dock and adapted to be
raised and lowered as described.
portion.
20. The dock set forth with reference to Figures 1, 2 and 3, consisting mainly
of the body constructed as described, gates A consisting of a plurality of arms
arranged and adapted to move about hinges in the horizontal plane, a front or
"fore-
gate
portion, and secondary half gates B, hinged at the end of said foregate
21. The dock set forth with reference to Figures 8, 9, 10 and 11, consisting mainly
of the body C, solid gates A having a plurality of secondary arms a hinged to said
gates, and a sill H extended in front of said gates, and the lower chambers or tanks
of the body C of the dock being also extended in front of said gates, in the manner
specified.
Dated this 19th day of December
Biber LAGAK
CHARLES JAMES FOX.
By Cheesbrough & Royston,
15, Water Street, Liverpool, Patent Agents.