Improvements in and relating to Manhole Covers, Chiefy Designed for Use with the Ballast Tanks of Vessels.
Year: 1887

page_text: Improvements in and relating to Manhole Covers, Chiefy Designed
for Use with the Ballast Tanks of Vessels.
1, PETER MITCHELL, of Greatham Terrace, West Hartlepool, in the county of
Durham Assistant Manager of Shipyard and Graving Docks do hereby declare the
nature of this invention and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement :-
My invention relates to manhole covers and to means for securing the same in
position, my improvements being especially applicable to the ballast tanks of vessels.
Heretofore the manhole covers of ballast tanks have been made substantially flat
and the cross bars or bridges used for securing the said covers in place have been
made convex externally so that the said cross-bars and their fastenings project
considerably above the ceiling" which is placed over the tanks.
2:
Owing to this projection of the cross-bars and their fastenings it has generally
been desirable when stowing cargoes of long materials such as rails or pipes to lay
packing or "dumage" say from two to three inches in thickness upon the ceiling so
as to raise the latter above the level of the cross bars and bolts, which arrangement
necessitates a considerable loss of stowage space. Also when unloading cargoes in
bulk the projecting cross-bars and bolts hinder the free use of shovels, scoops and
the like.
The object of my present invention is to obviate these disadvantages and to this
end it comprises the improvements hereinafter described.
In the accompanying drawing
Figure 1 is a plan of a door or cover and fastenings constructed according to my
invention.
Figure 2 is a sectional view of the same also showing portions of the tank and
ceiling, and
Figure 3 is a similar view to Figure 2 but at right angles thereto..
a is the door proper, which as shown, is creased or dished so as to have a concave
form externally and b, bare studs of ordinary construction.
c, c are the cross-bars or bridges which are bent or arched inwardly so as to cause
them to lie as low as possible, the ends of the said cross-bars being notched or recessed
[Price 6d.

page_text: at d, d as shewn in Figure 3 to fit over the edges e of the metal around the manhole
to prevent the cover from shifting.
,e are the nuts by means of which the cover is tightened and f, is the ceiling
which covers the top of the tank.
By means of this construction the various parts of the door are all brought below
the level of the ceiling so that a plate g, can be let into the same flush with its surface.
It will thus be understood that no packing or "dumage" is necessary and that cargoes
in bulk can be unloaded much more easily than heretofore as the shovels or the like
can be freely used.
Although I have described my invention as applied to ballast tanks it is to be
understood that it is also applicable in other cases where it is desired to keep a
manhole cover and its fastening as nearly as possible level with the surrounding
parts.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed 1 declare that what I
claim is :-
:-
A manhole cover and its fastenings constructed and arranged substantially as