Year: 1886

page_text: We WILLIAM HENRY LAIDLER and THOMAS LAIDLER Engineers both of Meldon
House N° 9 Leopold Street, Burdett Road Bow in the County of Middlesex 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:
Our invention relates to the measurement of a sector of a circle and our object
is to give the exact size form and shape of a sector of a circle and to indicate the
number of sectors required to. make up a complete circle also the diameter and
circumference of the same.
In accordance with this invention the body of the instrument has a circular
groove out into it to receive a circular ring, which is fitted to move freely in such
circular groove. On the top of the circular ring a square or rectangular bar is
fixed with a short side, and a long side, the latter has a pointer projecting out at
its extreme end which is allowed to move one quarter of a circle or 90 degrees.
On the long side of this square or rectangular bar and at its upper corner it is
marked with a scale indicating the measurement of circles. Extending from the
corner point of the rectangular bar and one inch down its side, the said bar is fixed
on the circle in such a position that when it is moved the end of the scale one inch
from the point really becomes a dead centre and never moves from its central
position when the circle to which the rectangular bar is fixed is moved backward
or forward from zero on the right to 90 degrees or the extreme limit of the
quadrant on the left. In describing the upper part of this rectangular bar with its
scale of circles we will hereinafter describe it as the right or moveable jaw.
At the extreme end of the pointer on the long side of the rectangular bar
and immediately beneath it on the body of the instrument is arranged a quadrant
scale commencing at the right hand side at or zero, and extending to the
opposite or left hand side to 90 degrees (separately marked thereon) completing one
quarter of a circle; this quadrant scale has also other numbers placed on it for the
purpose of denoting the number of sectors that will make a complete circle and in
further illustration we.. begin at the left hand side of the quadrant where it is
marked 90 degrees and bringing the pointer on the long side of the rectangular bar
-over this number the right jaw will have opened to its full extent and will show ·

page_text: of the quadrant and on this line will be found the number 4. When the pointer p
is brought to this mark the right jaw J¹ is full open 90 degrees and shows the
shape it will require viz 4 segmental pieces between the two radii to make a
complete circle and so on as the pointer is moved over the figures it indicates by
the jaw J the proper shape of the sector between the two jaws J¹ and J' likewise
the number of sections to make a circle.
The elevation in section Figure 2 is described and drawn on the line B¹ B" this
is marked in a similar manner and lettered as on the plan -line A¹ A". W is the
wood block to which all the parts are attached A the ring B the metal plate or
body with circular groove. S the rectangular bar attached to the ring A by means
of handle H screwed into it is the ivory quadrant let into the body of the
wood W over which the pointer p projecting over it passes freely cutting the marka
of degrees or numbers representing sectors of a circle.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is:-
First. The new or improved measuring gauge arranged with a moveable circular
ring with rectangular bar attached and formed with pointed end or pointer and
having measuring scales marked on the upper corners thereof all moving round
a dead centre thus producing a full and free opening the shape of a sector of a
circle arranged substantially in the manner and for the purpose herein before
described and represented in the drawings hereto annexed.
Second. We claim the fixed jaw with diameter scales marked thereon forming
radii on one side in conjunction or in combination with a moveable jaw forming
radii the shape of a sector of a circle substantially as described with reference to
the drawings hereto annexed.
.
Third. We claim the fixed quadrant Q with degrees marked thereon from zero
to 90 degrees and scales of numbers to indicate the number of sections required to
make a complete circle substantially as described with reference to the drawings
hereto annexed.
Dated this 6th day of August 1886.
TONGUE & BIRKBECK,
Agents for the Patentees.