IMPROVEMENTS IN PROTRACTORS
Year: 1885

page_text: I, WILLIAM FORD STANLEY, of 4 and 5 Great Turnstile, Holborn, in the County
of Middlesex, Mathematical Instrument, Maker, do hereby declare the nature of
my Invention for "IMPROVEMENTS IN PROTRACTORS" to be as follows:―
.The purpose of this invention is the improvement of the circular form of pro-
tractor generally used by Civil Engineers. The object of the invention is to bring
the two sides which subtend any given angle direct up to the angle which is
formed in the centre of the circle; for this object I make the protracting part of
the circular protractor of two flat rings fitted together so that one of the rings
may slide and revolve upon the other presenting a plain surface. Upon one of
the rings I divide the protracted circle in the ordinary manner to 360° and upon
the second ring I divide a vernier reading into this or a simple line only. From
one of the rings I carry a triangular plate of metal directed towards the centre of
the circle so that its acute point shall indicate this centre and one edge of this plate
or pointer shall coincide with 0 of the divided circle and form a line direct to the
centre. On the other ring which carries the vernier I carry a similar triangular
plate to that described above the point of which is at the centre of the circle and
one edge direct from this to the reading of 0 of the vernier or the single line.
By this means any angle may be measured by the two sides of the pointers
directly approaching it. Exterior to the circles I place a continuation of the
pointers or of one edge of them so as to continue the lines which subtend the angle
beyond the protracted rings. In place of two entire rings fitting to each other
I may use an undercut groove in one ring only and a sliding piece in the groove
to carry its pointer, or other mechanical equivalent. I also claim on the same
principles described to make a protractor of less than the complete circle as three
fourths or half a circle having one straight part or edge parallel to 0°. and 180º.

page_text: COMPLETE SPECIFICATION.
I WILLIAM FORD STANLEY, of 4 and 5 Great Turnstile, Holborn, London, do
hereby declare the nature of my said Invention for "IMPROVEMENTS IN PRO-
TRACTORS," and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
The purpose of this invention is the improvement of the circular form of pro-
tractor such as are generally used by Civil Engineers. The object of the invention
is to bring the two sides which subtend any given angle direct up to the angle
which is formed in the centre of the circle; for measuring this angle, for this object
I make the protracting part of the circular protractor of two flat rings fitted
. together so that one of the rings may slide and revolve upon the other presenting
a plain surface. Upon one of the rings I divide the protracted circle in the
ordinary manner to 360° and upon the second ring I divido a vernier reading into
this or a simple line only. From one of the rings I carry a triangular plate of
metal directed towards the centre of the circle so that its acute point shall indicate
this centre and one edge of this plate or pointer shall coincide with 0 of the divided
circle and form a line direct to the centre. On the other ring which carries tbe
vernier I carry a similar triangular plate to that described above the point of
which is at the centre of the circle and one edge direct from this to the reading
of 0 of the vernier.
By this means any angle may be measured by the two sides of the pointers
directly approaching it. Exterior to the circles I sometimes place a continuation of
the pointers or of one edge of them so as to continue the lines which subtend the.
angle beyond the protracted rings. In place of two entire rings fitting to each
other I may use an undercut groove in one ring only and a sliding piece in the
groove to carry its pointer, or other mechanical equivalent. I also claim on the
same principles described to make a protractor of less than the complete circle
as three fourths or half a circle having one straight part or edge parallel to 0°
and 180°.
Fig. 5 Section of Fig. 3.
Having now particularly described and ascertained the nature of my said
invention and in what matter the same is to be performed I declare that what
I claim is
ɔ
A protractor made in such a manner as that the angles subtended by it shall
approach by edges of rules right up to or near to the centre-the method by which
this is accomplished being fully described and shown on the drawings.
WM FORD STANLEY.