Improvements in and Apparatus for the Manufacture of Ophthalmic Lenses.
Year: 1897

page_text: Date of Application, 21st Oct., 1897-Accepted, 21st Oct., 1898
COMI LEIE DIECIFICATION.
Improvements in and Apparatus for the Manufacture of
Ophthalmic Lenses.
We, HENRY PORTER, of 7, Pall Mall, in the County of Middlesex, trading as
Cary & Co., Mathematical Instrument Makers and Ophthalmic Opticians, and
GEORGE HENRY ODELL, of 5, Fairland Road, Romford Road, in the County of Essex,
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 relates to ophthalmic lenses and a method of and apparatus for
producing them.
In shanking or shaping and grinding a simple ophthalmic lens to fit the frame in
which it is to be mounted, the workman has no guidance as to the position of the
optical centre, and must therefore either treat it as being perfectly central or else be
guided by his sense of touch, consequently the optical centre and the centre of the
frame are rarely coincident.
In the manufacture of a compound ophthalinic lens from a lens-blank of
plano-cylindrical form, the "plano" surface of the lens-blank being in the rough and
thick enough to enable the required spherical surface to be produced, the workman
who grinds the "plano" surface can not tell the exact position of the axis of the
cylinder if the latter be central, of course the centre of the spherical surface will
coincide with said axis; but, as the said axis is not always placed in the centre of the
square of glass or lens-blank upon which the cylindrical surface is ground, it frequently
follows that the centre of the spherical surface does not exactly coincide with that
axis, and the lens will then have two distinct optical centres.
A simple ophthalmic lens just before completion is according to our method -
mounted in a holder to have its refractive centre determined and the outline of the
frame it when finished is required to fit drawn round that centre by a marking tool
before said lens is given to the workman who fits it into the frame. The result is
that the refractive centre of the lens is placed exactly in the centre of the frame. In
a case where, however, the lens is required to have its refractive centre in a position
otherwise than central (to correct errors of convergence and divergence), we move
the holder by means of adjusting screws, which may have verniers, to enable any
desired position of the refractive centre of the lens to be attained to a decimal of a
millimetre, either up or down or out or in, before the marking tool is used.
In producing a compound ophthalmic lens according to our method, we employ
apparatus to determine when the axis of the cylinder of the lens-blank is horizontal.
This axis we bring coincident with the collimation line of the apparatus and then by
aid of a marking tool (having its axis on the collimation line) mark upon the lens-
blank an oval or other figure slightly larger than the frame the lens is eventually to
fit. The lens-blank is thereupon taken out of the holder and shanked to the mark
cut by the tool and given to the lens-worker to have the "plano" surface converted:
into a spherical one of the necessary power. If the lens be ordered with the axis of
the cylinder at any particular angle, before using the marking, tool and while said-
ixis remains horizontal we adjust a divided ring surrounding the holder until its zero

page_text: mark corresponds with the zero mark on the cell. We then rotate the holder (which
by friction takes the ring with it) until the divisions on said ring show that the axis
of the cylinder has been brought to the proper angle. We now with the marking
tool (adjusted to the size required) mark the shape of the frame on the lens-blank,
which is afterwards shanked to the mark and given to the lens worker to have the
spherical surface formed; the lens being finally ground to fit the frame.
By aid of apparatus made in accordance with our invention, we can determine
the optical centre of any simple lens used for ophthalmic purposes and mark the
shape required round that centre. We can also mark a compound lens-blank to
show the workman the position of the axis of the cylindrical surface so that he can
place the centre of the spherical surface coincident with said axis, so that the
said axis will come perfectly horizontal or in any particular meridian or degree
ordered, and so that the lens when mounted will be central in the frame. The main
features of our apparatus are an eye-hole in a plate, a frame with horizontal and
vertical wires crossed, a holder, a plate with horizontal and vertical slots crossed,
means for effecting adjustment of the holder, and a tool for marking the lens or the
· lens-blank after the adjustment.
Our invention will be readily understood by reference to the accompanying
drawings.
Fig. 1.is a diagram illustrating an ordinary lens or lens-blank (either simple or
compound) in side elevation.
Fig. 2 is a similar view giving an idea of what is seen through the eye-hole
of the apparatus when a compound lens-blank is mounted in the holder and
before said holder has been adjusted.
Fig. 3 gives an idea of what is seen after adjustment when either a simple lens
or a compound lens or lens-blank is mounted in the holder.
Fig. 4 shows the mark cut on the lens or lens-blank by the diamond point of the
marking tool to guide the workman in finishing said lens or lens-blank.
In Fig. 5, the refracted lines of light are omitted (therefore this view clear ly
illustrates the appearance of the product of our apparatus ready for handing to a
workman).
Fig. 6 represents the product after the edge has been ground away up to the
mark cut by the diamond marking tool.
Fig. 7 is a side elevation of our apparatus for ascertaining the refractive centre or
the axis of a lens or lens-blank and for holding said lens or lens-blank while it is
accurately marked.
Fig. 8 is a corresponding plan.
Fig. 9 is a transverse section on the line 1-1, Fig. 7.
Fig. 10 is an end elevation; the stage with the parts pertaining thereto having
been removed.
(Figs. 11 to 14 are drawn to a larger scale.)
Fig. 11 is a rear elevation of the holder for the lens or lens-blank and the stage
with the marking tool attached.
Fig. 12 is a corresponding longitudinal section.
Fig. 13 is a plan of the marking tool.
Fig. 14 is a view showing the marking tool partly in front elevation and partly in
section on the line 2-2, Fig. 12.
A is the lens or lens-blank and A is a mark cut by the marking tool.
B (Figs. 9, 11 and 12) is the holder. b are pieces of india-rubber secured to the
holder; being corresponding pieces of india-rubber on the lid B¹ of the holder.
The pieces b are fixed to spring-actuated plungers. The lid B₁ is hinged at b
(Figs. 7, 8 and 9) and is provided with a suitable fastening. The holder B is
surrounded by a ring B¹¹. The holder and the ring rotate in a cell B*. The
ring is ground into the holder and fits it tightly enough to move with it. B' is
a handle on the ring B for turning said ring while the holder remains
stationary. A milled head B3 has a spindle in a fitting on the cell B*; a
pinion b³ (Fig. 11) on the spindle gearing, with a circular rack 62 on the holder B.
3.

page_text: The cell B is united to a frame. B** that works between guides b' and b attached
to a carrier B*. A pinion b (Fig. 12) on the spindle of a milled head B³
(Figs. 7, 8, 9 and 11) mounted in a fitting 6° screwed to the carrier B* gears
with a rack b on the frame B**. B is a milled head on a spindle b' connected
to the carrier B. The spindle 6 has a screw-thread that engages with a
corresponding screw-thread in a fitting lying in a slot in a plate cl screwed to
a piece c² which is screwed to a stage C. The bar c³ is screwed to the plate c¹. The
plate 610 and the piece 611 are connected to the carrier B*. The stage C can be moved
along the base D by pulling or pushing the knob C'. It can be fixed in any desired
position by the clamp E. E¹ is the handle of the clamp. F is a plate screwed to the
front end of the base D and having an eye-hole F¹ (Fig. 10). G and G¹ are eye-pieces
The bar G2 is pivoted concentrically with. the eye-hole F and can be turned from the
position shown in the drawings through an angle of 180°. The eye-piece G is fixed
on the bar G2, but the eye-piece G¹ is a dummy and slides on said bar.
(These eye-
pieces though convenient are not essential.) H is a frame with wires h¹ and h² that
cross at h. It is clamped to the stage C by the thumb-screw K screwing into the
piece c². His a ring-handle for use in removing or replacing the frame. L is a
plate screwed to the rear end of the base D and containing slots L' and L2 which cross
at (Fig. 7). By means of screws clearly shown in Figs. 7, 8 and 9, the wires h¹
and h can be adjusted until the point h is in line with the eye-hole F¹ and the
point . M is the diamond point of the marking tool, and M¹ is the plunger in which
said point is fixed. m is the barrel wherein the plunger works, and m¹ is the spring
that urges said plunger forward. m¹¹ is a catch for holding the plunger M¹. The
barrel m is secured to a plate m² which is mounted on a slide M2. The milled
head M has a spindle m³ that rotates in a projection on the end of the slide M²; a
screw-thread on the spindle engaging with a screw-thread in a slot in a projection on
the end of the plate m². There is a cross pin through the arms of the slot to lock
the spindle m³, The slide M² is provided with guides m and works along the
piece M, which is fixed to the end of a shaft M5. The bridge m is screwed to the
guides m' on the slide M². A roller Me has a spindle m³ which passes through a slot
in the piece M. One end of the spindle has a bearing in the slide M2 and the other
end has a bearing in the bridge m³. A plunger m" actuated by a spiral spring m² in a
casing m presses upon the slide M². m³ is the bearing for the shaft M. This bearing
is fixed to a plate M7. M³ is the handle for turning the marking tool and m¹º is the
thumb-screw by which said handle is secured to the shaft M. N and N¹are templates
on a collar N* which is slid over the bearing m³ and held by a pin n. The lower half
of the ring B" is divided to degrees. The guide 68 is divided to decimals of millimeters
and there is a vernier at V on the frame B**. The plate 610 of the horizontal adjustment
is also divided to decimals of millimeters and has a vernier. The sliding plate m² is
divided so that it can be seen what size of mark the tool will cut on the lens or lens-blank.
When a simple ophthalmic lens is mounted in our apparatus, we operate in the
following manner :-We take the lens-A and place it in tire holder B and close and
fasten the lid B¹. The lens is then firmly held between the pieces of india-rubber b
and b. A sight is thereupon taken through the eye-hole F1; and the crossed
wires h¹ and h² are seen and also the refracted lines of light and 12 from the crossed
slots L1 and L2. It is usually necessary for the refractive centre (that is, the point
where the lines of light 11 and 12 cross one another) to be on the collimation line
(that is, on the straight line which runs from the eye-hole F¹ through the points h
and ). The milled head B can be manipulated to bring the line coincident
or parallel with the wire h' and the milled head B to bring the line 12 coincident
or parallel with the wire h². Fig. 3 gives a clear idea of what might be seen
through the eye-hole F1 after the manipulation of the milled heads B5 and Be
(the lid B of the holder. and other parts of the apparatus except the wires h¹
and h² are omitted in the diagram). The operator can adjust the dummy eye-piece G¹
until it is the proper distance from the eye-piece G. The eye-pieces are shown in
the correct position for an operator that uses the right eye in sighting; the duinmy

page_text: eye-piece G¹ saving him the necessity of closing his left eye. When an operator
desires to use his left eye for sighting, the bar G2 is turned over, whereupon the
eye-piece G saves him the necessity of closing his right eye. The refractive
centre of the lens having been brought on the collimation line, or up or down
or out or in as may be specially ordered, the thumb-screw K is released and the
frame H removed by aid of the ring-handle H The marking tool is then con-
nected to the piece c² on the stage by said thumb-screw K. The catch m" is
thereupon turned to release the plunger M¹. When the handle M³ is revolved;
the diamond point M cuts a mark A* on the lens. The roller M runs round.
the template N and determines the shape of the mark A*. The size of the mark
may be varied by turning the milled head M³ and taking the diamond point M
nearer to or bringing it further from the axis of the shaft M5. The spring m and
plunger m by acting on the slide M² cause the roller M to follow closely the outline
of the template N. The template N¹ is a duplicate of the template N, and can be
employed by reversing the collar N*. When it is desirable to change the templates N
and N¹ and replace them by others of different shape, the marking tool is removed
from the apparatus and the thumb-screw m10 is unscrewed and the shaft M³ withdrawn
from the bearing m°. The collar N* can then be easily pulled off the bearing and
another collar with different templates substituted.
When a compound ophthalmic lens-blank is mounted in the apparatus, the lines
and 2 will probably appear through the eye-hole F¹ as indicated in Fig. 2. The
milled head B3 is then turned until the lines and 12 are vertical and horizontal.
The line is then brought on the collimation line by manipulating the milled
head B5. The frame H is afterwards removed and the marking tool connected to
the stage C by the thumb-screw K. An oval or other figure slightly larger than the
frame having been marked on the lens-blank, said lens-blank is taken out of the
holder for the spherical surface to be formed; the lens being then finally ground to
fit the frame. If the lens be ordered. with the axis in any particular meridian, before
using the marking tool the divided ring B is moved by the handle B² until its
zero coincides with the zero mark on the cell B*. While moving the divided ring,
the holder is not disturbed. The milled head B³ is thereupon turned until the divisions
on the ring B show that the desired position has been reached. The oval or other
figure is then marked on the lens-blank.
The accuracy of the instrument may be tested as indicated below:-The vertical
and horizontal adjustinents having been placed at zero, then if the point h be on
the collimation line the wires h¹ and h² will be seen exactly in the centres of the
slots L¹ and L2. If the wire h¹ bisect the empty holder B and the wire h² also
bisect said holder, it foliows that the centre of the holder is on the collimation line.
If the axis of the bearing m³ of the marking tool be on the collimation line, the
slot L¹ will bisect the empty bearing me and the slot L2 will also bisect said empty
bearing. If the pin n be withdrawn, the slot L² should bisect the hole that said pin
occupied. If there be another hole for the pin n on the other side of the bearing,
the slot L2 should bisect both holes.
The apparatus we have illustrated in the accompanying drawings is given by way
of example only, as it will be obvious many variations may be made.
Having now particularly described and ascertained the nature of this inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is
-
1. An ophthalmic lens or lens-blank having a mark drawn upon it to show the
position of its refractive centre or its axis, substantially as described.
2. The method of ascertaining the refractive centre or the axis of an ophthalmic
lens or lens-blank and putting on a mark for the guidance of the workman in
finishing the lens or lens-blank substantially as set forth.
3. Apparatus for ascertaining and marking the refractive centre or the axis of an
ophthalmic lens, or lens-blank, substantially as illustrated in the accompanying
drawings.

page_text: 4. For ascertaining and marking the refractive centre or the axis of an ophthalmic
lens, or lens-blank, apparatus comprising an eye-hole, horizontal and vertical wires
crossed, a plate containing horizontal and vertical slots crossed, means for holding
and adjusting the position of the lens or lens-blank, and a marking tool, substantially
as described.
5.. Means for holding and adjusting the position of the lens or lens-blank
substantially as illustrated in the accompanying drawings.
6. A marking tool substantially as illustrated in Figs. 11 to 14 of the accompanying
drawings.
1011
COLL
ions
JAMES W. SMALLMAN,
Nuneaton,
Agent for the Applicants.