Improvements in Refractometers for Testing the Eye-sight.
Year: 1892

page_text: Date of Application, 19th Dec., 1892-Accepted, 18th Mar., 1893
COMPLETE SPECIFICATION.
Improvements in Refractometers for Testing the Eye-sight.
I, WILLIAM HENRY DOUGLAS, of Stourbridge in the County of Worcester,
Watchmaker 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 consists in the construction of a compound refractometer which
may also be used as a simple refractometer. I form the refractometer by placing a
double series of cylindrical glasses and a double set of spherical lenses between two
discs constructed so as to form a box enclosing them. This box works round a
centre-pin carried upon an outer fixed plate.
The cylindrical glasses are placed within one side of the box with their axes
pointing to the centre of the disc, and placed opposite openings pierced in the side
of disc; the spherical lenses are placed within the other side of the box with holes
pierced opposite to them in that disc.
This box is covered on each side by discs covering the holes and working upon
the before named centre pin.
These outer discs are each pierced with a hole and are attached together at this
point by an eye-piece, so as to form a sight hole. The before named outer plate
with the centre pin through it is a fixed disc carried upon a suitable adjustable
stand.
This fixed disc has engraved or otherwise indicated upon it a double scale of
degrees so placed, that the eye-piece can be brought up to any desired point on the
scale, by revolving the outer discs to the required extent upon the centre-pin. The
eye-piece is then fixed in position by means of a nut pressing upon the discs. The
box containing the cylinders is then moved round the centre pin, so that the series
of cylinders are passed before the eye-piece in rotation, until the correct cylinder
is reached. An opening below the eye piece is made through the outer disc to
expose the number indicative of each cylinder, each having its number placed
below it on the disc.
A spring click pressing into indents in these discs beneath each lens adjusts it
correctly to the eye-piece.
The disc containg the spherical lenses can be passed before the eye-piece in a
similar way to that described for the cylindrical glasses, one of the holes in each of
the inner discs being left empty to enable the sets to be used singly or combined.
Two nuts are placed on the edges of the discs, so that each disc may be held whilst
the others are left free to turn.
Similar results may be obtained by fixing a series of cylindrical glasses in slides
and making them pass a central hole in a plate upon which a double scale of
degrees is engraved or otherwise indicated. These slides are passed through a
guide fixed upon a smaller plate which is made to revolve on a hollow centre upon
the fixed or larger plate.
An arrow engraved or otherwise indicated upon the smaller plate shows the
vertical position of the guide and cylinders. The plate can then be turned to
bring the cylinder which is opposite the central hole to any angle required, the
arrow thus pointing to the same on the scale.
The plate and guide can then be fixed in position by a binding screw. Openings
in the guide piece show the number or dioptric of the lens.
A similar guide is fixed in a horizontal position on the other side of the fixed
plate, through which to pass, before the centre hole, spherical lenses in series.

page_text: A click on the side of each of the guides falling into indents on the slides ensures
the lenses being in correct position.
Each of these refractometers may be mounted on an adjustable stand.
Referring to the accompanying drawings in which similar letters of reference
relate to similar parts upon the various figures―
Figs. 1 & 2 are views of each side of the refractometer described in the first part
of this Specification.
Fig. 3 is a sectional view of the same.
Fig. 4 is a view of one of the inner discs forming the box.
Figs. 5, 6 & 7 are front, back & sectional views of the second form of the
refractometer described in this Specification and
Fig. 8, a view of a slide for carrying lenses.
(a) is the centre-pin round which the several discs turn, (b) is the fixed plate
having upon it the scale (c), marked with a double set of degrees. (d), Fig. 3 is
the section of the box containing the cylindrical glasses showing through holes (d³)
in the disc (d') and with the spherical lenses showing through openings (d') in the
disc (d). Fig. 4 shows one of these discs with the holes (d³) for the lenses. (e) is
the disc covering one of the pierced sides of the box (d), and (f) is the disc
covering the other side of the box (d). (g) Figs. 1, 2 & 3 is the eye-piece attaching
the two discs (e) and (f) together at the point where they are pierced, so as to form
a sight hole. (h) is the spring click which drops into the indents. (i), Fig. 4,
and (2) the click on the other disc to drop into similar indents on the other pierced
plate so that when the glasses or leuses are brought opposite the eye-piece (g), the
click will hold them in a central position. (j) and (¹) are the openings below the
eye-piece for exposing the number or dioptric of each glass or lens, when turned
round into position. (k) is the nut to press upon the discs and keep them in
position. (1) and (¹) are nuts on the edge of the discs which upon being screwed
down on to either disc will hold that disc and leave the others free to turn.
In order to enable either of the sets of cylindrical glasses or spherical lenses to
be used separately one of the holes (d³) of each of the discs (d) and (d) is left
empty so as to leave a clear opening through the sight-hole, and thus not interfere
with the glasses or lenses on the other disc, as they are brought round to the eye-
piece. (m) is the upper part of an adjustable stand.
Referring to the other description of refractometer which forms part of this
invention and to which Figs. 5, 6, 7, & 8 relate, (y) is the large fixed plate upon
which is the double scale (c) indicating degrees and (2) is the smaller plate revolving
on the hollow centre or eyelet (*), and having indicated upon it the arrow or
pointer (p). (w) is the guide piece upon the smaller plate through which to pass
the slide, shown at Figure 8, for carrying the cylindrical glasses, and passing them
in front of the central hole or eye-piece (¹). Thus by turning the small, plate
round its centre, the guide-piece (w), with the slide therein, can be brought to any
required angle, the arrow indicating the degree at the same time. (k¹) is a binding
screw to keep the plate in position. (2) (³) are openings in the guide-pieces
through which the dioptric or numbers represented on the lenses will show, and
which openings may be above and below the centre-hole (a³). (v) is the guide
piece fixed in a horizontal position on the other side of the fixed plate (y), through
which to pass before the central hole (2) a slide carrying spherical lenses in series.
(h) & (h³) are spring clicks catching into indents on the edges of the slide.
Compound or simple refractometers may thus be obtained by either of these
methods described and illustrated.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be perforined 'I declare that what I
claim is,
.
1st. The application of a movable eye-piece to refractometers with cylindrical
lenses, to govern the angle at which the cylinders pass the eye-piece consecutively.

page_text: 2nd. The application of a revolving guide carrying slides to refractometers with
cylindrical glasses, to govern the angles at which the cylinders pass the eye-piece
consecutively.
3rd. Obtaining simple or compound refractometers substantially as herein set
forth and illustrated.
Dated this 8th day of December 1892.
HENRY F. TALBOT,
7, Cherry Street, Birmingham, Agent for the Applicant.