IMPROVEMENTS IN INSTRUMENTS OR APPLIANCES FOR MEASURING CURVES
Year: 1878

page_text: LETTERS PATENT to Edward Robert Dale, of Glanville's Wootton, in the
County of Dorset, for the Invention of "IMPROVEMENTS IN INSTRUMENTS OR
APPLIANCES FOR MEASURING CURVES."
ealed the 7th May 1878, and dated the 17th January 1878.
PROVISIONAL SPECIFICATION left by the said Edward Robert Dale at the
Office of the Commissioners of Patents on the 17th January 1878.
EDWARD ROBERT DALE, of Glanville's Wootton, in the County of Dorset.
PROVEMENTS IN INSTRUMENTS OR APPLIANCES FOR MEASURING CURVES."
*
IM-
I measure the curvature of circular arcs forming portions of cylinders, spheres, or
curved objects generally, and exhibit therefrom in a simple manner, and by mere
inspection, without calculation, their several principal dimensions and properties,
that is to say, the radius, diameter, circumference, area, cubic contents, weight, &c.,
by means of an instrument, the subject of this my Invention, and which I term a
" curve meter."
This instrument is intended to answer the general purposes of "callipers," than
which however it is much more universal in its application, more convenient in use,
and more comprehensive in its indications.
The principle upon which the action of the apparatus in taking measurements is
based is that of intercepting a chord of known length forming such circular curve,
measuring its versed sine, and indicating by means of a properly constructed scale
the several dimensions named above, all of which can be deduced or calculated from
the length of the versed sine.
The instrument is formed of two principal parts, each performing its distinct
function. By the first part of the apparatus the length of the verse sine is accurately
ascertained; and by the second the measurement so ascertained is magnified in
extent and caused to actuate an indicating finger or pointer.
When intended for general measurements I form the measuring part of the
instrument with two projecting fingers, each terminating in small carefully rounded
points, or so-called "knife edges." These points or knife edges are directed radially

page_text: towards an imaginary point equidistant from each of them, and forming in effect
the centre of a circle, the mean size, or thereabouts, that the instrument is intended
to measure. So constructed, these points, when the instrument is applied to a
circular curve, form the limits of the chord; that is to say, an imaginary line
between these two points is the chord of known length previously referred to.
The versed sine or distance from the middle of this imaginary line to the periphery
of the curve is measured by means of a third finger or point placed midway between
the two fixed points, moveable in a direction at right angles to the chord, and
whose zero position is such that the imaginary line joining the two fixed points
runs through the third or moveable point.
When the instrument is applied to a flat surface the three points come in the
same straight line, but when the instrument is applied to a curved surface the
middle or moveable point is forced out of the straight line to an extent corre-
sponding with the curvature. If the curve is convex the point is moved to one side
of the imaginary line, and if concave to the opposite side.
The moveable or sliding point is continued through the stem of the instrument,
and terminates at the other end in a rack, which gearing into a small pinion placed
on an arbor or axis, also carrying an indicating finger, magnifies the motion and
exhibits the result upon a suitable scale.
The indicating part of the instrument is formed as a dial or clock-faced disc. I
prefer to make the dial with two faces, and to employ two indicating fingers, one
face and finger being marked to serve for concave measurements, and the other for
convex.
In order to render one instrument capable of measuring through a wide range of
sizes I sometimes make the jaw of the instrument carrying the fixed points
removeable, so that several jaws carrying points capable of subtending ares of
different dimensions may be applied to one and the same instrument.
In some cases also with a view of equalizing the indications I construct the rack
so as to gear into an excentric pinion.
In other cases I find it advisable to further magnify the verse sine length by a
wheel and pinion, or a series of wheels and pinions, actuated by the first motion
pinion, this last modification of my Invention being chiefly required for instruments
measuring large diameters.
Although generally two fixed points are sufficient, yet in the case of instruments
intended for the measurement of spheres, hollow cones, truncated cones, or hemi-
spherical cups, I find it convenient to employ three fixed points.
Sometimes also I propose to combine or form the instrument with two compass
points, one fixed and the other moveable, for the measurement of circles or plane
figures.
Also a moveable dial may be placed behind the fixed or main dial, having
numbers which may be turned so as to show through small openings or slots in the
main dial; for instance, 2 on the main dial; by turning the dial behind it would
show 2, 4, &c., making it 22, 44, &c.
The jaw of the curve meter may be made to propel from or towards the centre
of the curve meter by rack and pinion, a screw, or any suitable contrivance, and
may be arranged so that by moving it, the moveable dial at the back of the main
dial will turn and show a certain number, according to the distance the jaw is
moved towards or from the centre of the curve meter. By any suitable contrivance
this moveable dial and jaw, or jaws, may be retained in any desired position.
Another jaw may be used at right angles to the main jaw, and forced outward from
the centre of the curve meter for the purpose of insuring the curve meter being
placed at right angles to a line of centre of a cylinder, or imaginary line through the
centre of any curve.

page_text: .
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Edward Robert Dale in the Great Seal Patent Office on the 13th May
1878.
EDWARD ROBERT DALE, of Glanville's Wootton, in the County of Dorset.
PROVEMENTS IN INSTRUMENTS OR APPLIANCES FOR MEASURING CURVES."
"
IM-
I measure the curvature of circular ares forming portions of cylinders, spheres,
and curved objects generally, and exhibit therefrom in a simple manner, and by
mere inspection, without calculation, their several principal dimensions and
properties; that is to say, the radius, diameter, circumference, area, cubic contents,
weight, and so forth, by means of an instrument, the subject of this my Invention,
and which I term a "curve-meter."
This instrument is intended to answer the general purposes of callipers, than
which however it is much more useful, being more universal in its applications,
more convenient in use, and more comprehensive in its indications.
The principle upon which the action of the instrument is based is that of inter-
cepting a chord of known length, forming part of such circular curve, measuring its
verse sine, and indicating by means of a properly constructed scale the several
dimensions named above, all of which can be deduced or calculated from the length
of the verse sine.
The instrument is formed of two principal parts, each performing its distinct
function. By the first part of the apparatus the length of the verse sine is accurately
ascertained; and by the second the measurement so ascertained is magnified in
extent, and caused to actuate an indicating finger or pointer.
When intended for general measurements I form the measuring part of the
instrument with two projecting fingers, each terminating in a small carefully rounded
point, or so-called "knife edge.' These points or knife edges are directed radially
towards an imaginary point, equidistant from each of them, and forming in effect
the centre of a circle the mean size, or thereabouts, that the instrument is intended
to measure. So constructed, these points, when the instrument is applied to a circular
curve, form the limits of the chord; that is to say, an imaginary line between these
two points is the chord of known length previously referred to. The distance from
the middle of this imaginary line to the periphery of the curve is measured by
means of a third finger or point placed midway between the two fixed points,
moveable in a direction at right angles to the chord.
When the instrument is applied to a flat surface the three points come in the
same straight line, but when the instrument is applied to a curved surface the
middle or moveable point is forced out of the straight line to an extent corre-
sponding with the curvature. If the curve is convex the sliding point is moved to
one side of the imaginary line, and if concave to the other side of that line.
The moveable or sliding point is continued through the stem of the instrument,
and terminates at the other end in a rack, which gearing into a small pinion placed
on an arbor or axis, also carrying an indicating finger, magnifies the motion and
exhibits the result upon a suitable scale.
The indicating part of the instrument is formed as a clock-faced disc or dial, and
I prefer to make this dial double or with two faces, and to employ two indicating
fingers, one face and finger being used for concave measurements, and the other for
convex measurements.
In order to render one instrument capable of measuring through a wide range of
sizes I sometimes make the jaw of the instrument removeable, so that other jaws
subtending arcs of different dimensions may be applied to one and the same
nstrument.
The principal forms of
"
my curve meter" are illustrated by the Drawings accom-
panying and forming part of this Specification.
The points A and B in Figures 1 to 7 are the two fixed points previously referred
o; C is the third and moveable point.

page_text: In the form of instrument illustrated by Figures 1, 2, 3, 4, and 5 the movement
of the point C is made to indicate the diameters, circumferences, areas, &c., as before
mentioned, by means of an index finger I, moving round a dial L, as shown in
Figure 4. The point C is here kept in its normal position by a helical spring D
acting on a collar E. When the three points A, B, C, are in the same straight line
the index finger stands at the zero point F.
In some cases with a view of equalizing the indications I construct the rack to
gear into an excentric pinion.
In some cases also I find it advisable to further magnify the movements of the
point C by a wheel and pinion, or a series of wheels and pinions. In Figure 1, for
example, I employ a curved rack H gearing into an excentric pinion M. In
Figure 2 I show a plain rack H gearing into a plain pinion M, but the wheels N
and O are excentric wheels. In Figure 3 a plain rack H, hinged at N, is kept in
gear with an excentric pinion M by means of a spring S. The spindle P is kept
from twisting round by its lower part G, being squared, as shown.
Figs. 6 and 7 show a smaller and simpler form of the "curve meter," in which
the pointer I attached to the spindle P moves over a scale marked on the edge of
the case containing P. In place of a spring the finger pressed against the head H
will serve to keep the point C against the article to be measured.
Figures 8 and 9 represent a form of the instrument for use as a wire gauge. The
rod or wire, the diameter of which is required, is placed in the ring E, when the
rise of the spindle D, and.consequently of the rack A which gears into the pinion B,
causes the pointer C to indicate the diameter on the dial.
Although generally two fixed points are sufficient, yet in the case of instrume ts
intended for the measurement of spheres and other such forms I find it convenient
to employ three fixed points.
Sometimes also I propose to combine or form the instrument with two compass
points, one fixed and the other moveable, for the measurement of circles or plane
figures.
Having thus described the nature of my said Invention, and the manner in which
the same is or may be carried into effect, I wish to state that I do not confine or
restrict myself to the precise details or arrangements which I have thought it
necessary to describe and delineate, as many variations may be made. therefrom
without departing from the main or essential features thereof; but I do claim as
my Invention the instrument or instruments constructed and acting substantially
as herein described.
DADE TUTT