An Improved Mathematical Instrument for Measuring and Laying Down Angles.
Year: 1897

page_text: Date of Application, 9th June, 1897
Complete Specification Left, 9th Mar., 1898-Accepted, 20th May, 1898
PROVISIONAL SPECIFICATION.
An Improved Mathematical Instrument for Measuring and Laying
Down Angles.
I, ARTHUR MARINUS ALEXANDER STRUBEN, of 4, Albert Hall Mansions, Kensing-
ton Gore, in the County of London, Civil Engineer, do hereby declare the nature
of this invention to be as follows:-
-:
This invention relates to an improved mathematical instrument for measuring
and laying down angles and has reference more particularly to what are known as
bevel protractors wherein an arm moves over a graduated scale or protractor.
An important feature of my said invention consists in making the movable arm
of such a width that it extends from the centre up to or beyond the outer edge of the
protractor, one of its edges being therefore radial and the other parallel to such
radial edge.
A further important feature consists in that, whereas the graduations on the
protractor of my improved instrument extend only through ninety degrees they are
numbered in such a manner as to enable readings from zero to 360° or infinity to
be taken. I may further provide a vernier or index on the movable arm to facilitate
the reading of small angles.
The
According to one construction of my improved mathematical instrument the
protractor proper is furnished with a fixed arm forming an extension or prolonga-
tion of the base thereof the longitudinal edges of such arm being parallel to one
another. The movable arm is capable of turning through a right angle.
pivot of the movable arm may be hollow and may consist of a flanged ring resem-
bling an enlarged eyelet. A glass or other transparent plate on which the centre of
the protractor is marked may be fitted in the said pivot ring.
The vernier may be applied to the movable arm in any convenient manner, and
the zero mark on the protractor is placed opposite the central or zero division of the
vernier. The said zero mark on the protractor need not coincide with the base
line thereof, as in ordinary protractors, and the ninety degree mark is similarly out
of coincidence with the vertical line from the centre. Four sets of numbers may be
provided on the protractor, each set corresponding to the angles of one of the quad-
rants of a circle. In this case a convenient mode of numbering the graduations would
be as follows:-One set of numbers extends from 0 to 90. Another from 180 to 270.
A third set commences with 270 on the 90° mark and finishes with 360 on the zero
mark, and a fourth set commences with 90 on the 90° mark and finishes with 180
on the zero mark. The two last sets may be printed upside down to enable them
to be read off easily when the protractor is being used in an inverted position.
The protractor arc may be only of the size absolutely necessary to accommodate
the aforesaid graduations, this size in such case being usually a little larger than a
quadrant.
In some cases the instrument is provided with a clamping device whereby the

page_text: movable arm can be locked in any position to which it has been set and then the
instrument answers the purpose of an adjustable set square.
Dated this 9th day of June 1897.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.
An Improved Mathematical Instrument for Measuring and Laying
Down Angles.
I, ARTHUR MARINUS ALEXANDER STRUBEN, of 4, Albert Hall Mansions, Kensing-
ton Gore, in the County of London, Civil 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 relates to an improved mathematical instrument for measuring
and laying down angles and has reference more particularly to what are known as
bevel protractors wherein an arm moves over a graduated scale or protractor.
An important feature of my said invention consists in making the movable arm
of such a width that it extends from the centre up to or beyond the outer edge of the
protractor, one of its edges being therefore radial and the other parallel to such
radial edge.
A further important feature consists in that, whereas the graduations on the
protractor of my improved instrument extend only through ninety degrees they are
numbered in such a manner as to enable readings from zero to 360° or infinity to
be taken. I may further provide a vernier or index on the movable arm to facilitate
the reading of small angles.
In order that the invention may be clearly understood and readily carried into
effect I will proceed to describe the same by aid of the accompanying drawing
which illustrates one form of my improved mathematical instrument.
a is the protractor proper which is furnished with a fixed arm 6 forming an
extension or prolongation of the base thereof, the longitudinal edges of such arm
being parallel to one another.
c is the movable arm which has the two parallel edges d d the former being the
radial one above referred to.
In the example shown this arm is formed also with two segmental portions c¹³
which are useful for striking small curves. The said arm is capable of turning
through a right angle on its pivot e which latter may be hollow as shown and may
consist of a flanged ring resembling an enlarged eyelet. A glass or other
transparent plate f on which the centre g of the protractor is marked by cross line
may be fitted in the said pivot ring.
h is the vernier which may be applied to the movable arm in any convenient
manner, the zero mark on the protractor being placed so that it comes opposite the
central or zero division of the vernier, when the two arms of the instrument are
closed together. The said zero mark on the protractor need not coincide with the
base line thereof, as in ordinary protractors, and the ninety degrees mark may
similarly be out of coincidence with the vertical line from the centre or vice versa.
Four sets of numbers may be provided on the protractor, each set corresponding to
the angles of one of the quadrants of a circle. A convenient mode of numbering
the graduations is shown in the example illustrated in which one set of numbers
extends from 0 to 90, another from 180 to 270, a third set commences with 270 on
the 90° mark and finishes with 360 on the zero mark, and a fourth set commences
with 90 on the 90° mark and finishes with 180° on the zero mark. The two last

page_text: sets may be printed upside down to enable them to be read off easily when the
protractor is being used in an inverted position.
The protractor arc may be only of the size absolutely necessary to accommodate
the aforesaid graduations, this size in such case being usually a little larger than a
quadrant.
The instru-
In some cases the instrument is provided with a clamping device i whereby the
movable arm can be locked in any position to which it has been set.
ment then will answer the purpose of an adjustable set-square.
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. An instrument for measuring or laying down angles, comprising essentially
two members one of which has a protractor graduated as hereinbefore described and
the other of which is pivoted centrally to the protractor substantially as and for
the purposes specified.
2. An instrument of the kind referred to having as its pivot a flanged ring or
eyelet with or without a transparent plate on which the centre of its protractor is
marked, substantially as described
3. A mathematical instrument for measuring and laying down angles, having its
parts constructed arranged and operating substantially as hereinbefore described
with reference to the accompanying drawings.
Dated this 9th day of March 1898.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.