An Improved Combination Instrument for Mathematical Drawing, Setting Out Angles, and for similar purposes
Year: 1893

page_text: COMPLETE SPECIFICATION.
An Improved Combination Instrument for Mathematical Drawing,
Setting Out Angles, and for similar purposes.
WILLIAM HENRY BROWN 101 Greville Road Bristol, S. Leveling and Drawing
Instruments Manufacturer 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 instrument consists of two movable limbs secured by a centre joint, and
being hinged in such a manner as to make two pairs of legs or blades, and adjustable
by a set screw, it is designed to do the whole of the work at present done with set
squares, roof-pitches batters, protractors sectors with greater dispatch and
accuracy.
When open the instrument gives the angles 45° and 90° and when closed it gives
30° 60° and 90° without adjustinent.
By means of the protractor graduations shown on joint, the instrument can be
adjusted to any degree, not already provided for by its shape namely 30°, 45°, 60°,
and 90°, and consequently any line or series of-lines of any inclination can be drawn
as readily by the use of this instrument as from an instrument made to the particular
inclination desired.
As the instrument consists of two triangular limbs of shape shown in drawings
and hinged together at such a point as to form two pairs of blades or legs it will be
seen that as the pair of long blades or legs "E" are opened or closed the pair of
short legs or blades "F" must move in a fixed proportion to same, and also the
transverse distances contained between either pair of blades or legs must vary in
like proportion. Thus, used as a sector, when the pair of long legs or blades "E"
are applied to the line it is desired to divide, the transverse distance, between any
pair of indications as shown on edge of the legs or blades "E," is noted, and the
transverse distance between the corresponding pair of indications, as shown on the
small pair of legs "F" will divide the line into the number of parts as shown by
the power engraved on joint against which the edge of the blade cuts.
Thus supposing as an example that it is desired to divide a finite line into two
parts the instrument is adjusted so that the edge of the blade "E" cuts indication
marked "2" engraved on the centre joint, then the line to be divided must be
placed transversely between the pair of long legs or blades "E" and supposing the
numbers shown on either side of the long blades to be "7" then the transverse
distance between the same numbers "7" on the pair of short legs or blades "F"
will give the power of 2 or one half the distance shown by long legs
"E."
Referring to drawings:
"
Fig. 1 shows the instrument as a set square set at 90°. "a is a metal quadrant
joint acting on centre "c" and having screw "6" to hold it in position at any
required angle. "EE" are pair of long legs or blades "F F" pair of short legs
or blades.
The plate is slotted at "d" to permit of screw "6" passing through it. This
joint may be graduated for use as a plain protractor, and also for use as a sector
after the manner shown in drawings and herinbefore described.
Fig. 2 shows a section through instrument at A-B.
Fig. 3 shows the instrument as a set square inclined to the horizontal at 45°, the
vertical angle being 90°.
Fig. 4 shows the instrument as a set square giving the angles 60° and 90°, the
vertical angle being 30°.
Fig. 5 shows the instrument in use as a sector set at the power of 2 and also

page_text: The pair of long legs are shown on drawings marked “E E” and the pair of
short legs are marked "F F."
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 new and improved mathematical drawing instrument consisting of two
triangular shaped blades or legs, of wood steel, vulcanite or other suitable material,
hinged together by a metal joint in such a manner that when the long legs "E" are
closed together the outline of the instrument will give the angles 60° 90° and 30° and
when the short legs "F" are closed together the angles 45° and 90° are obtainable;
with or without the indications and graduations on blades and centre joint fitting
the instrument for use as a proportional sector as a plain protractor.
and
or
2. A metal joint "a" of circular or other convenient form, with or without one
edge being graduated for use, in conjunction with the blades or legs, aforementioned,
as a plain protractor.
Also with or without indications fitting the joint for use, also in conjunction
with the blades or legs, as a proportional sector.
3. Two pairs of blades or legs with graduations and indications as shown in
drawings hinged together in such a manner as to produce, in conjunction with
engraving on centre joint a complete proportional sector, giving results at sight
without the use of mathematical formulae or constant continual or repeated bi-section;
substantially as shown in drawings and herein before described.
Dated this 26th day of April 1893.
W. H. BROWN.