Improvements in Measuring Instruments for Spectacles and the like.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
Improvements in Measuring Instruments for Spectacles and the like.
I, JOHN THOMAS GRADON, of 140, Kingston Road, in the City of Oxford, Ophthal-
mic Optician, do hereby declare the nature of this invention to be as follows:-
This invention has for its object the production of an instrument for measuring
the various parts of spectacles such as the height of the bridge, the "in or out
measurement of the bridge, the pupillary distance and also for finding the inclina-
tion of the axis of a cylindrical lens.
According to this invention one edge of a rule, which may conveniently be
15 centimetres long and 20 millimetres broad, is graduated in millimetres. A
line is ruled down the centres and the marks denoting 5, 6 and 7 centimetres are
continued to this line; the space between these lines is set out in millimetres
thus forming a convenient measure for taking the pupillary distance. The rule
is also marked for measuring the height of the bridge.
On the other edge of the rule is a semicircular ring marked in degrees; it may
conveniently be 8 millimetres wide and its inner diameter 60 millimetres. At
the centre of the ring there is a small projection on the edge of the rule.
On the face of the rule a narrow strip is inserted capable of being slidden up
above the top edge of the rule. The strip carries at its top end a pin which pro-
jects on both sides of it, the distance the pin projects back being such that when
the strip is in its lowest position the back of the pin is flush with the back of
the rule,
Dated this Twenty-first day of September 1897.
- COMPLETE SPECIFICATION.
Improvements in Measuring Instruments for Spectacles and the like.
I, JOHN THOMAS GRADON, late of 140, Kingston Road; in the City of Oxford,
and now of 18, Broad Street, Oxford, Ophthalmic Optician, 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 the production of an instrument for measuring
the various parts of spectacles, such as the height of the bridge, the "in or out
measurement of the bridge, the pupillary distance and also for finding the inclina-
tion of the axis of a cylindrical lens.
"
The drawings attached to the specification show an instrument made in accordance
with this invention.
Figure 1 is a plan of a measuring instrument.

page_text: Figures 2, 3, 4 and 5 are diagrammatic views showing the manner in which
the instrument is used.
1 ..
One edge of the rule a, which may conveniently be 15 centimetres long and
20 millimétres broad, is graduated in millimetres.
A line is ruled down the centre and the marks denoting 5, 6 and 7 centimetres
are continued to this line, the space between these lines is set out in millimetres,
thus forming a convenient measure for taking the pupillary distance.
The rule is marked at a¹ for measuring the height of the bridge.
On the other edge of the rule a is a semicircular ring 6 marked in degrees,
it may conveniently be 8 millimetres wide and its inner diameter 60 millimetres.
At the centre of the ring b is a small projection c on the edge of the rule.
On the face of the rule a narrow strip d is inserted capable of being slidden
up above the top of the rule. The strip d carries at its top end a pine which
projects on both sides of it, the distance the pin projects back being such that
when the strip is in its lowest position, the back of the pin is flush with the back
of the rule.
The manner in which the angle of inclination of the axis of a cylindrical lens,
when the lens is in a spectacle frame, is found, is as follows:-
Place the spectacle frame containing the lenses in the position shown in Figure 2,
and having brought the middle of both end pieces exactly over the centre line of the
rule, make the marks I, I¹ with ink or a writing diamond. The marks may be
dispensed with if the spectacle frame be placed on the centre line of the rule,
as described above, and the distance which the bridge, where it is joined to the
eye wires, is above or below this line be noted. It can be measured by placing
it in the position shown in Figure 2. Next, take the instrument with the
ring 6 to the right, and place it between the first and second fingers of the left
hand. Now put the spectacle frame in the position shown in Figure 3, and hold
what is now the right hand edge of the rule parallel to some distant straight
edge, e.g. the upright bar of a window frame f (Figure 3). Owing to the prism-
atic effect of the cylinder the test object as seen through the lens will now appear
to be out of line with the rest as can be seen at Figure 3.
Next, keeping the point on the edge of the lens, exactly over the centre k
of the ring b, rotate the opposite end of the frame around this point as a centre
until the whole of the test object is exactly in line as can be seen, in Figure 4.
Now read off the degree on the ring b which is immediately underneath the
point I (Figure 4), and the degree at which the axis of the cylinder is placed in
its eye wire can be found by the following rules: -
I. If the point I be on the plus side of the scale, the axis of the cylinder will
be placed in its eye wire exactly as many degrees below this point as this point
itself is above zero of the scale.
II. If the point I be on the minus side of the scale, the axis of the cylinder
will be placed in its eye wire exactly as many degrees above this point as this
point itself is below zero of the scale.
Or, III. The axis of the cylinder will be placed in its eye wire at a degree which
is at right angles to the degree found by Rule I or II.
.
Rule III is required because the test object g can be brought into line when
the axis of the cylinder is perpendicular as well as when parallel to a line drawn
from the centre of the ring b to zero.
The manner in which the "out" measurement of the bridge of a spectacle
frame is taken is as follows:
Place the front of the spectacle frame flat against the back of the rule, with
the end pieces and projections of the bridge if there are any-slightly above the
top of it. Next, push up the strip d (Figure 5) until the pin e comes in con-
tact with the middle of the bridge. By this means the measurement can be taken
much more accurately than it otherwise could be.
"
The "in measurement of the bridge can be taken in the same way, but with
the back of the spectacle frame placed against the back of the rule.

page_text: 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:
Measuring instruments for spectacles and the like substantially as described
and shown in the drawings.