Improvements in or Appertaining to Protractors or Instruments for Plotting Angles.
Year: 1888

page_text: Date of Application, 23rd May, 1888
Complete Specification Left, 23rd Feb., 1889
Complete Specification Accepted, 6th Apr., 1889
- PROVISIONAL SPECIFICATION.
Improvements in or Appertaining to Protractors or Instruments for
Plotting Angles.
I, JOHN FLETCHER, of Rock House, Ulverston in the County of Lancaster, Mining
Engineer, do hereby declare the nature of this invention to be as follows :--
This invention has for its object a protractor that will act as an ordinary protractor
with much more convenience than those now in use, and that will also enable one
after finding an angle to at once draw a line at that angle some distance from tho
place where the angle was originally found.
For this purpose I form a ring graduated in the usual manner of protractors with
the scale of angles shown in degrees both ways. Inside this and sliding upon it I
form a diametric piece with a vernier at each end sliding on the interior face of the
outside circle. This diametric piece is provided with two milled rollers keyed to
the same shaft, one roller being at each end of the shaft with their faces projecting
a little below the face of the diametric piece and their axis being parallel with the
diametric edge.
In this way the whole apparatus becomes at once a parallel ruler. The diametric
edge is provided with a scale, but I prefer to have this scale movable, so that I can
take it out and put other scales in its place. The movable scales have their zero
point at the centre, and are graduated each way.
The result is that I can take an angle from any given point, or line and transfer it
by the parallel ruler arrangement to some distance off, instead of having to first mark
out the line and then by means of a parallel ruler or set-square and straight-edge
transferring the line to its right position.
The article can be made in ebonite, brass, aluminium or other metal.

page_text: Improvements in or Appertaining to Protractors or Instruments for
Plotting Angles.
I, JOHN FLETCHER, of Rock House, Ulverston in the County of Lancaster, Mining
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 has for its object a protractor that will act as an ordinary protractor
with much more convenience than those now in use, and that will also enable one,
after finding an angle, to at once draw a line at that angle some distance from the
place where the angle was originally found.
The invention will be besi described by aid of the accompanying drawings in
which,
Figure 1 is a plan view of the protractor.
Figure 2 a section on line A B of Figure 1, and
Figure 3 a section on line CD of Figure 1.
In these A is a ring graduated in the usual manner of protractors with a scale of
angles A shewn on the drawing round one quadrant of the circle. The graduations
may extend from 0 degrees to 90 degrees each way, or may be continued round the
circle from 0 degrees to 360 degrees or both graduations, one exterior to the other may
be employed. Inside the ring A, I form a diametric piece B, which rotates upon the
shoulder formed on the interior side of the outside ring A and is prevented from
falling out of the said ring by the retaining strips CC. The diametric piece B is
provided at each end with a vernier E.
The diametric piece B, being held in a given position, the graduated ring A may
be thus turned about it by hand as desired. When a fine adjustment is required the
ring A is connected to the piece B by a clamp D and micrometer screw d¹. The.
clamp is held fast by the screw d and the ring adjusted as desired by the screw d'.
By using the screw in conjunction with the verniers E, a most exact adjustment of
the ring may be obtained. The diametric piece B is provided with two milled
rollers F of equal diameter after the manner of a parallel ruler. The rollers are
keyed to the same shaft F¹, one roller being at each end of the shaft with their
peripheries projecting a little below the face of the diametric piece B and the ring A
and their axes being parallel with the diametric edge B¹.
In this way the whole apparatus becomes at once a parallel ruler. The diametric
edge B is provided with a scale B but I prefer to have this scale movable, so that
I can take it out and put other scales in its place. The movable scales have their
zero point at the centre and are graduated each way.
I am thus enabled to take an angle from any given point or line and transfer it
by the parallel ruler arrangement to some distance off instead of having to first mark
out the line and then by means of a parallel ruler or set-square and straight edge
transfer the line to its right position.
The article can be made in ebonite, brass, aluminium or other metal.

page_text: Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be perfornied, I declare that what I
claim is :-
1. The improved instrument for plotting angles or the like, consisting of an inner
diametric pièce B having a diametric and preferably graduated edge B¹, of an outer
annular protractor A mounted upon the piece B and capable of being revolved about
the same in proximity with the plane of the paper and of a pair of synchronously
moving milled rollers F of equal diameter mounted one at each end of the said
piece B with their peripheries projecting slightly below the level of the same and of
the ring A, substantially as and for the purposes set forth.
2. In combination with the diametric piece B and the annular protractor revolvable
thereon, one or more verniers E carried by said piece and located in proximity to
the graduations on the protractor A, and a suitable micrometer adjusting device such
as D d d' for effecting the accurate angular adjustment of the protractor, substantially
as set forth.
3. The improved combination instrument, constructed as a whole substantially as
shown and described, whereby angles may be plotted and transferred from one point
to another without the aid of a separate parallel ruler, straight edge and set square,
or similar device.