Improvements in or connected with Ohart Tables for Navigational Purposes.
Year: 1889

page_text: Date of Application, 4th May, 1889
Complete Specification Left, 4th Feb., 1890-Accepted, 8th Mar., 1890
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PROVISIONAL SPECIFICATION.
Improvements in or connected with Ohart Tables for Navigational
Purposes.
I, SAMUEL MANNING of St. Leonards Villa Victoria Road Surbiton in the County
of Surrey Master Mariner do hereby declare the nature of this Invention to be as
follows:
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My Invention has for its object to provide chart tables which can he used with
facility not only for protecting the chart but for enabling the user to lay off the ship's
course whilst the chart is protected by the table According to my Invention I make
the top of the table of a transparent material such as glass which is comparatively
thin and which has its outer side so prepared as to present a surface which will enable
markings to be made thereon whilst not so interfering with the transparency of the
glass or the like as to impede the observation of the chart therethrough. This
preparation of the outer surface may be effected in any suitable way for instance by
means of hydrofluoric acid, or by treatment with sand emery powder emery paper or
the hike and in order to increase or restore the transparency of the glass or the like
treated as aforesaid and still retain the desired surface for marking upon. I may use
a material or mixture of materials which will have the desired effect A suitable
mixture is one of turpentine with a small proportion of oil.
Dated this 4th day of May 1980
J. H. JOHNSON & Co,
47, Lincoln's Inn Fields, London, Agents
COMPLETE SPECIFICATION.
Improvements in or connected with Ohart Tables for Navigational
Purposes.
I SAMUEL MANNING of St. Leonard's Villa Victoria Road Surbiton in the County
of Surrey Master Mariner 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
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My Invention has for its object to provide chart tables which can be used with
facility not only for protecting the chart but for enabling the user to lay off the
ship's course whilst the chart is protected by the table.
According to my Invention I make the top of the table of a transparent material
such as glass which is comparatively thin and which has its outer side so prepared as
to present a surface which will enable markings to be made thereon whilst not so
interfering with the transparency of the glass or the like as to impede the observation
of the chart therethrough.
The accompanying Drawing represents in section an apparatus made in accordance
with my Invention. A is a frame of wood or other suitable material of the size and
shape to accommodate the charts. It has in its upper side a groove 6 of a depth
such as to receive the glass C the frame not projecting beyond the surface of the
glass so that therefore the rules or instruments employed in laying off the ship's
Course can be moved freely over the whole top of the table. D is a backing board
which has around its edges a tongue & which engages under a corresponding tongue f
formed around the inside of the frame A. e are fastenings consisting of buttons
centered to the backing board D and securing it in place by being turned into notches
in the inner side of the frame A.
I do not limit myself to the precise form of the fitting of the backing board to the
frame for instance it may be made by a double groove and tongue as shewn at ƒƒ³ hh'

page_text: in figure 2. The backing board and its fastenings should be situated within the line
of the lower side of the frame so as to allow the frame to rest evenly upon the surface
on which it may be placed.
It is the outward surface of the glass which is prepared in the manner herein-
before mentioned. The preparation as before stated should be such as to give a
surface which receives the mark of a black lead pencil for instance but is not such
as to prevent the markings on the chart being properly visible through the glass.
The preparation may be effected by roughing the surface by some such material as
emery but as this would interfere with the proper transparency of the glass it should
be repolished sufficiently to bring back the required degree of transparency, or it may
be done by treatment with acid the latter plan being preferable This may be done
by carefully cleaning and drying the glass and then applying wax or the like round
the edge to give a shallow trough into which the acid may be run. The glass around
the edges may be painted with Brunswick black to retain the wax when applied.
A suitable composition for this edging is pitch with a little Russian tallow mixed
with it. A suitable acid is that known in commerce as "white acid" (white hydro
Fluoric acid). The acid remains on the glass until the glass will just take a fine lead
pencil mark (usually about from 3 to 20 minutes according to the strength of acid
will be long enough for the acid to act). The acid is then poured off and the wax
margin removed and the glass thoroughly washed and dried. The glass is then
secured in the frame A which may be done by bedding it in red lead cement
placed in the groove b. The chart is placed on the backing board D with the
face of the said chart upwards and then it and the said board are placed in position
and the board is secured by the buttons e the chart occupying the space g.
If emery or the like be used to roughen the surface of the glass and its
transparency is thereby too greatly interfered with I may increase. or restore the
transparency and still retain the desired surface for marking upon by running over
the surface turpentine with a small proportion of oil.
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.
A chart table or holder and protector made substantially as described and provided
with glass or the like with a surface prepared so as to receive pencil or like marks
but not so as to obscure the markings of the chart beneath substantially as herein-
before described.
L 11
1
P T 1
1000