Year: 1898

page_text: I, WILLIAM MULLAN, of Marlborough Park, Belfast, in the County of Antrim,
Engineer, do hereby declare the nature of this invention to be as follows:-
This invention has for its object an improved form of man-hole cover and means
for securing the same for use in the double bottoms of ships and other like structures.
Hitherto when it has been found necessary to have the bolts of the man-hole not to
project above the ordinary line of surface a curb or double flanged angle iron
has been placed round the man-hole and two plates or a plate and dogs have been
used.
Now my invention is designed to avoid the use of this very expensive double
flanged angle iron curb and yet arrange it so that the fastenings are below the
general surface.
In carrying out my invention, I form both the dogs and the man-hole cover
preferably of iron or steel plates stamped or pressed into shape by hydraulic or other
pressure between suitable dies. The central portions of both the man-hole cover
and the dogs are dished or set downwards sufficiently to allow of the ends of the
securing bolts and the nuts thereon being below the level of the plating of the double
bottom in which the man-holes are fitted, thus avoiding the necessity for using
the aforesaid flanged rim. The man-hole cover is formed with a flange projecting
beyond the man-hole all round for a short distance and between the man-hole plate and
this flange is the usual joint of spun yarn, white lead, or other material. The man-
hole cover has a spigot or projection all round fitting against the edge of the
man-hole so as to keep the man-hole cover in place and to hold the cover from lateral
displacement. The cover is dished from this spigot down to the necessary depth and
the two bolts are preferably rivetted into it. The dog consists of a smaller plate
dished in a similar manner but not to so great an extent and with raised portions
round the bolt holes extending across for strengthening purposes. It is preferably
made in one piece and afterwards cut in two across the centre. In fixing the jointing
material is first placed on the man-hole cover, it is then drawn up into place by hand
and held there while one of the dogs is placed in position and the nut screwed up
until it is thoroughly tight. The other dog is then placed in position and screwed
up. In thus describing my invention I would point out that I do not bind myself
to this exact arrangement. It is obvious that the man-hole cover and even the dogs
can be made of cast iron or malleable wrought iron or other metal; that the dogs
instead of being a complete dished plate cut in half can be two broad girders or
bars enlarged round the bolt hole and of sufficient strength to withstand the requisite
pressure; also that it is not absolutely necessary to corrugate the dogs even when
they are made of a single plate; also that the dishing of the man-hole cover need
not be plain, but can also be corrugated in such manner as to strengthen the section

page_text: while lessening the quantity of material used; further, that in some cases a single dog
and a single bolt can be used instead of two bolts the dogs in such case having
preferably a spigot or its equivalent to keep it in position, while if the dog consists of
a dished plate, a large hand hole or hand holes are preferably made in it when
only one bolt is used so that the hand can easily grasp the bolt through the hole
in the dog.
Improvements in or relating to Manhole Covers.
I, WILLIAM MULLAN, of Marlborough Park, Belfast, in the County of Antrim,
Engineer, 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 :---
This invention has for its object an improved form of manhole cover and means
for securing the same for use in the double bottoms of ships and other like structures.
Hitherto when it has been found necessary to have the bolts of the man-hole not to
project above the ordinary line of surface, a curb or double flanged rim has
been placed round the man-hole and two plates or a plate and dogs have been
used.
Now my invention is designed to avoid the use of this very expensive double
flanged rim and yet arrange it so that the fastenings are below the general
surface.
The invention will be understood from the following description, reference being
had to the accompanying drawings in which :-
Figure 1 is a cross section ;
Figure 2 a plan ;
Figure 3 a cross section showing a slight modification;
Figure 4 a plan thereof.
The manhole covers herein illustrated are especially suitable for the inner plating
of double bottomed vessels, being specially designed for ships in which the wooden
ceiling of the tank top has been dispensed with and the plating left bare. In such
case it is necessary that the studs and nuts for securing the doors should be below the
level of the plating in order to prevent them being damaged by or causing damage to
cargo. By my invention this has been accomplished without the use of expensive
double flanged or other rims hitherto used, thus effecting a considerable saving
in the cost.
In the drawings A is the manhole cover, B and C the dogs and D the plating. Both
the dogs and manhole cover are preferably of iron or steel plates stamped or pressed
into shape by hydraulic or other pressure between suitable dies. The central portions
of both the manhole cover A and the dogs B and C are dished or set downwards suffi-
ciently to allow of the ends of the securing bolts band cand the nuts thereon, being below
the level of the plating of the double bottom in which the manholes are fitted, thus
avoiding the necessity for using the aforesaid flanged rim. The manhole cover A is
formed with a flange a projecting beyond the manhole all round for a short distance,
and between the manhole plate D and this flange a is the usual joint E of spun yarn,

page_text: white lead or other material. The manhole cover has a spigot or projection a¹ all
round fitting against the edge of the manhole so as to keep the manhole cover A in
place and to hold the cover from lateral displacement. The cover A is dished from
this spigot down to the necessary depth, and the two bolts b and c are preferably
rivetted into it. The dogs consist of the plates B and C dished in a similar manner
but preferably not to quite so great an extent, and with raised portions 6¹ and c¹ round
the bolt holes for strengthening purposes. The dogs are preferably made in one
piece and afterwards cut in two across the centre at F.
In fixing, the jointing material E is first placed on the manhole cover A. The
cover A is then drawn up into place by hand and held there while one of the dogs B
is placed in position on opposite side of plating, and the nut on the stud b screwed
up until it is thoroughly tight. The other dog C is then placed in position and
screwed up.
In thus describing my invention, I would point out that I do not bind myself to
this exact arrangement. In Figures 3 and 4 for example the dogs B and C may be
recessed or dished round the bolt holes to sufficient depth to allow the nuts to lie
below the level of the dogs, the dogs in such case being strengthened by the webs G.
Further that in some cases a single dog and single bolt can be used instead of two
bolts, the dogs in such case having preferably a spigot or its equivalent to keep them in
position, while if the dog consist of a dished plate, a large hand hole or hand holes
are preferably made in it when only one bolt is used, so that the hand can easily
grasp the bolt through the hole in the dog. It is obvious that the manhole cover
and even the dogs can be made of cast iron or malleable wrought iron or other metal ;
that the dogs instead of being a complete dished plate cut in half can be two broad
girders or bars enlarged round the bolt hole and of sufficient strength to withstand
the requisite pressure, also that it is not absolutely necessary to corrugate the dogs
even when they are made of a single plate; also that the dishing of the manhole
cover need not be plain but can also be corrugated in such a manner as to strengthen
the section while lessening the quantity of material used. By dispensing with
wooden ceilings, shipowners save the first cost of thein, also the cost of repairs in
moving and replacing the same for surveys, while the double bottom plating being
accessible for cleaning there is much less corrosion than what usually takes place below
ceilings. The weight of the ceiling and the space it occupies are also saved which
in the larger class of vessels means a gain in dead-weight carrying capacity of from 50
to 70 tons and in measurement of from 80 to 100 tons of 40 feet. The dogs and
cover owing to their special shape are both exceedingly stiff, thereby ensuring a
perfect tight joint and affording a sufficient support to the edges of the opening.
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 manhole door composed of a cover dished out or set downwards in its central
portion seated against one side of the plating, a dog or dogs seated against the other
side, and dished out or set downwards sufficiently to allow of the ends of the securing
studs and the nuts thereon being below the level of the said plating, and studs passing
through both the dogs and the cover with their securing nuts contained in the set
down portion of the dogs, whereby a tight joint between the plating and the cover
can be obtained, whilst the ends of the studs with their nuts being below the level
of the plating prevents them being damaged or causing damage, substantially as
described.
2. In a manhole door, the combination of the dished cover A having a spigot or
projection all round fitting against the edge of the manhole so as to hold the cover
from lateral displacement, the dished dogs B, C or their equivalent, and studs passing
through both the dogs and the cover with their securing nuts contained in the dished-
out portion of the dogs, the dogs having raised portions round the stud holes for
strengthening purposes or not as required, substantially as described.

page_text: 3. The manufacture of manhole covers and dogs for the manhole openings in the
inner plating of double bottom steamers, made of iron, steel or the like stamped or
pressed by hydraulic or other pressure between dies (or cast) into the form substan-
tially as herein described, and for the purposes set forth.
Dated the 28th day of June 1899.
WM. P. THOMPSON & Co.,
Patent Agents, of Liverpool, Manchester, Birmingham and London.