COMBINED PROTRACTOR AND SCALE
Year: 1884

page_text: I THEODORE FREDERIC SANDBACHI TINNE of Briarley Aigburth Liverpool in
the County of Lancaster Engineer, do hereby declare the nature of my said
Invention for COMBINED PROTRACTOR AND SCALE 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 a method of so combining a protractor and a part scale
with a stock as to furnish for the use of Land surveyors and others an instrument
of great utility as regards compactness convenience and correctness in uso, as well
as economy of time in laying off angles in plotting surveys or in making other
mathematical drawings.
In the accompanying drawings Fig: 1 shews the upper side of the instrument,
and Fig 2 a section through the centre line A. B. of Fig 1, and the following letters
of reference indicate the same part of the instrument in both figures.
C. D is one of a set of interchangeable scales of ivory or other material divided
from each end into any number of proportional parts, and being true and straight
on the divided edge. It is attached by the two thumb screws E. F. to a semi-
circular protractor G. H. I. K. which has an extension of its plane on its straight
side towards G H for the purpose of receiving the scale and thumb screws above
mentioned This protractor is attached to the stock m. m. n. n. by the pivot L
about which it revolves through 180 degrees, carrying the part scale with it.
The stock M. M. n. n is in the form of an inverted T. It can be made in one
pieco or the part M M can be secured to the part N N by rivets or other means.
The stock has a hole and pivot at L by which the protractor G HIK, is pivotted
to it and it has a hole at OP through which the degrees marked on the edge of
the protractor can be seen-On one edge of the hole O. P. is a vernier under or in
contact with which slides the divided edge of the protractor. In a recess under
the stock there is rivetted to it at Q a flat spring R which presses the edge of the
protractor against the inner side of the stock and so prevents the protractor
revolving about the pivot L. Into the spring R is rivetted a button headed pin S
which projects through the stock m. m. Pressure on the head of this pin releases
the edge of the protractor from the restraint of the spring R. and allows the
protractor to revolve.freely.
In using the instrument the part of the stock N N rests or slides against the
sides of a T square blade or parallel ruler as shewn in Figs 2 and 3-The button S

page_text: being pressed down the spring R leaves the protractor free to be revolved so as to
bring the edge C. D. of the part scale to any relative angle with the edge N N of
the stock, the angle being shewn by the index and vernier at O P. Pressure being
taken off the button S, the spring R. firmly holds the protractor and stock in the
relatively angular position in which they have been placed-The whole instrument
being thus slid along the T square or ruler in a direction that may be called East
and west while the T square or ruler is moved in a direction that may be called
north and south, the point "zero" at either end of the part scale can be brought to
any point on a plan from which a measured line is to be projected-The instrument
being then held firmly down a measured line can be drawn of any desired length
within the limits of the scale with the certainty of its being in the correct angular
direction already set on the vernier index.
If necessary a tangent screw and binder may be used in place of or in addition
to or in continuation with the spring and button shown at R and S, so as to
facilitate the finer adjustment of angles by the vernier.
The instrument may also be made in the modified form shewn at Fig: 5 which
shews the extended edge G H of the protractor I K as resting against the ruler
while the part scale C D attached to the stock M N revolves about it.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1. The combination of a part scale and protractor with a stock as herein
described, and illustrated in the accompanying drawings.
2. I also claim the spring R and Button S as applied to a protractor for the
purpose of holding it in position in connection with a straight edge or ruler.
Dated 20th Antahan 1001